ii TABLE OF CONTENTS Page LIST OF FIGURES ........................................................................................................... iii LIST OF TABLES ............................................................................................................. iv NOMENCLATURE ........................................................................................................... v ACKNOWLEDGMENTS ................................................................................................. vi ABSTRACT ...................................................................................................................... vii CHAPTER 1. INTRODUCTION ....................................................................................... 1 CHAPTER 2. BACKGROUND and SUPPORTING RESEARCH ................................... 2 CHAPTER 3. PROJECT APPROACH .............................................................................. 4 CHAPTER 4. REQUIRED PROJECT MATERIALS ....................................................... 6 CHAPTER 5. PRINTING PROCESS DEVELOPMENT .................................................. 8 CHAPTER 6. SOLAR CELL TESTING.......................................................................... 12 CHAPTER 7. SOLAR CELL PRINTING AND TESTING CHALLENGES ................. 15 CHAPTER 8. RESULTS AND DISCUSSION ................................................................ 18 CHAPTER 9. CONCLUSION AND FUTURE WORK .................................................. 23 Bibliography ..................................................................................................................... 25 APPENDIX A. PRINTER TURN ON, PRINT PATTERNS, AND JETTING WAVEFORMS ................................................................................................................. 26 APPENDIX B. PRINTING PROCESS INSTRUCTIONS .............................................. 30 APPENDIX C. MATLAB IV SCRIPT ............................................................................ 55 APPENDIX D. INK SYNTHESES .................................................................................. 58 iii LIST OF FIGURES Page Figure 2.1 Solar Device Structure [7] ................................................................................. 3 Figure 3.1 Dimatix Materials Printer DMP-2850 Lab ........................................................ 5 Figure 5.1 PEDOT:PSS Printer Set-Up .............................................................................. 9 Figure 5.2 Ag Test Pattern ................................................................................................ 10 Figure 5.3 Fully Printed Solar Cell Example .................................................................... 11 Figure 6.1 Calibrated Solar Cell IV Curve ....................................................................... 13 Figure 6.2 IV Curve for a Fully Printed Solar Cell........................................................... 14 Figure 8.1 Solar Cell 1 IV Curve With Light On ............................................................. 19 Figure 8.2 Solar Cell 1 Light Source Off IV Curve .......................................................... 19 Figure 8.3 Solar Cell #2 IV Curve Characteristics ........................................................... 20 Figure 8.4 Solar Cell #3 IV Curve Characteristics ........................................................... 21 Figure 8.5 Solar Cell #4 IV Curve Characteristics ........................................................... 21 Figure 8.6 Solar Cell #5 IV Curve Characteristics ........................................................... 22 iv LIST OF TABLES Page Table 5.1 Printing Parameters from Mitra et al [7] ............................................................. 9 Table 5.2 Developed Printing Parameters ........................................................................ 10 Table 8.1 Solar Cell Performance Characteristics ............................................................ 22 v NOMENCLATURE IV Current-Voltage ZnO Zinc Oxide Ag Silver P3HT Poly-3-Hexyl Thiophene PCBM (6,6)-phenyl-C60-butyric acid methyl ester BHJ bulk heterojunction PEDOT:PSS Poly (3,4-ethylenedioxythiophene) Polystyrene Sulfonate PEN Polyethylene Naphthalate DMP Dimatix Material Printer OPV Organic Photovoltaics Voc Open Circuit Voltage Isc Short Circuit Current ELH Halogen Reflector Lamp vi ACKNOWLEDGMENTS I would like to thank my committee chair, Dr. Jackson, and my committee members, Dr. Rabosky, and Dr. West for their guidance and support throughout the course of this design project. I would also like to thank Dr. Burnett for the help and support. In addition, I would also like to thank my friends, colleagues, and the department faculty and staff for making my time at Weber State University a positive experience. vii ABSTRACT Recent advancements in inkjet technology have enabled the material printing of semiconductor devices. Due to potential cost reduction and simple design customization, inkjet printing has become a significant field of semiconductor research. The purpose of this design project was to develop a solar cell printing process, fabricate the solar cell using the Dimatix materials printer (DMP)-2850, and evaluate the performance of the cell. A solar cell printing process based on existing research was developed. Multiple layers of material ink were deposited on a glass substrate using the DMP-2850 materials printer. The organic solar cell stack structure consists of four different material layers. Each material layer required unique printing parameter settings to produce the desired patterns. Throughout the fabrication process, the solar cell was heated on a hot plate between material layer printing. The developed printing process was implemented to produce functional solar cells. The performance of the solar cell was evaluated using an electronic heat lamp (ELH) light source, Keithley source meter, and current-voltage (IV) software on a computer. The solar cells were exposed to the light source and a voltage-current sweep was performed. Voltage vs current plots were obtained using the IV software. The voltage-current curves depict the open-circuit voltage and closed-circuit current of the solar cells. The developed printing process has successfully been utilized to fabricate fully printed solar cells. The evaluation process characterized the open-circuit voltage and closed-circuit current of the solar cells when exposed to a specific light source. The developed printing process will serve as a baseline for further solar cell research at Weber State University. 1 CHAPTER 1. INTRODUCTION Solar energy is a well-documented potential source of sustainable energy. Organic photovoltaics (OPV) are a particular category of solar cells, that involve the use conductive organic polymers. Some of the benefits associated with OPV solar cells are solution processability, device flexibility, and weight reduction. OPV solar cells are known to be more environmentally friendly when compared to many other classes of solar cells. According to the national renewable energy laboratory the highest recorded power conversion efficiency for an organic solar cell is 18.2% [1]. The highest recorded power conversion efficiency for a fully inkjet printed organic solar cell is 4.73% [2]. Typical semiconductor devices are fabricated in large-scale semiconductor fabs, that involve an extensive and costly fabrication process. In recent years, advancements in inkjet material printing technology has opened doors to fully printed semiconductor devices. Due to the potential fabrication simplicity, design customization, and cost reduction, inkjet materials printing of semiconductor devices has become an important area of research. The purpose of this project is to study and implement the material printing of solar cells. A solar cell printing process was developed. Process parameters were adjusted and different material layers were investigated. A solar cell was designed and printed and the fabricated solar cell demonstrated functional solar cell performance characteristics. Performance measurements of the printed solar cell were documented and compared to existing results. 2 CHAPTER 2. BACKGROUND and SUPPORTING RESEARCH In the past decade, several methods have been developed by researchers to print organic, perovskite, and dye-sensitized solar cells [3] [4] [5] [6]. The authors of “All- Inkjet-printed, All-Air-processed Solar Cells” demonstrated that functional solar cells can be fabricated using inkjet technology [3]. The solar cells were fabricated using inkjet technology to deposit multiple layers of material on a glass substrate. Materials were heated at temperatures up to 120 degrees Celsius between depositing material layers. Chen and Yen [2] developed a similar design procedure for solar cell design fabrication utilizing inkjet technology. The Dimatix Materials Printer has been utilized to fabricate dye-sensitized solar cells [3]. Many of the researched solar cell printing techniques share the same core procedure. Materials are deposited on a substrate and heated for a particular time and temperature [3] [4] [5]. Several publications on solar cell printing support that this printing method can produce functional solar cells. Previous research did not provide enough detailed information to develop a printing process using the Dimatix DMP-2850 materials printer. A more recent research article by Mitra et al [7] provides much more detailed information on using the a DMP- 2831 printer to fabricate fully printed solar cells. This research article is partially based on the research results of Jung et al [3]. A solar cell printing process was developed based on the research article “Manufacturing of All Inkjet-Printed Organic Photovoltaic Cell Arrays and Evaluating Their Suitability for Flexible Electronics” [7]. The organic solar cell stack structure consists of four different material layers. The fourth/top anode layer is poly (3,4- 3 ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS). The third/bulk heterojunction (BHJ) layer is made up of donor polymer-based poly-3-hexyl thiophene (P3HT) and acceptor (6,6)-phenyl-C60-butyric acid methyl ester (PCBM). The second electron hole transport layer is zinc oxide (ZnO) and the first/bottom layer is silver (Ag). Figure 2.1 below depicts the stack structure of the solar cell, material layer pattern dimensions, and the complete solar cell device. For the purpose of this project glass slide substrates were used instead of the flexible polyethylene naphthalate (PEN) substrates used by Mitra et al [7]. PEN substrates are expensive because they are flexible and very resistant to heat. PEN substrates can be heated to temperatures up to 200°C without significant substrate shrinkage. Glass substrates were used to reduce overall project cost. Image B of Figure 2.1 depicts the different material pattern dimensions. The dimensions shown on the far right of image B where the top and bottom contacts have an active area of 17.5mm2 were used for this design project. Image C of Figure 2.1 shows a top view of the complete solar cell device. Figure 2.1 Solar Device Structure [7] 4 CHAPTER 3. PROJECT APPROACH Weber State University’s Electrical & Computer Engineering Department has acquired a Dimatix Materials Printer DMP-2850. This printer has the capability to print conductive materials stored in disposable piezo inkjet cartridges on various substrates. Several vendors synthesize conducting and semiconducting material printer inks. For the purpose of this project inks were selected from Sigma Aldrich. The dry materials required to synthesize the donor-acceptor layer ink were obtained from Ossila. A solar cell design process was developed based on existing research [1][4]. Printing patterns were directly modeled after patterns developed by Mitra et al [7]. Because each material ink has specific physical properties, unique printing parameters were required for each individual ink. Printing parameters and cartridge settings developed by Mitra et al were used as a template [7]. Multiple layers of material were deposited on a glass substrate using the DMP- 2850 materials printer. A glass substrate was chosen to reduce the design project cost. Flexible heat resistant substrates can cost hundreds of dollars. Throughout the fabrication process, the solar cell was heated on a hot plate between material layer printing to evaporate any remaining solvent. The heating temperature and time duration was modeled after the heating process developed by Mitra et al [7]. 5 The performance characteristics of the solar cell were observed. The solar cells were exposed to a light source and a voltage-current sweep was conducted. The performance was documented and compared to existing results. Figure 3.1 Dimatix Materials Printer DMP-2850 Lab 6 CHAPTER 4. REQUIRED PROJECT MATERIALS From the time that the initial project research was conducted and the project was proposed, it was clear that funding would be required for materials to make this design project possible. Because this project required several material inks, single use disposable ink cartridges were required to print the different material layers. Material inks can cost five hundred dollars for 50mL of ink. Dimatix one-time use, disposable ink cartridges cost approximately one hundred dollars per cartridge. The Dimatix materials printer is manufactured by the company Fujifilm. Fujifilm is the only known vendor for Dimatix ink cartridges. A hot plate was required to heat the device in between material layer printing. The project also required various lab equipment such as wafer tweezers, syringes, filters, and glass substrates. An itemized budget was developed and a grant was written to obtain approximately four thousand dollars of funding for the project. The grant was approved and the required project materials were purchased. Approximately half of the budget was used to buy twenty Dimatix ink cartridges. The rest of the budget was spent on material inks, material to make inks, and miscellaneous lab equipment. Because the budget was limited, only project critical materials were purchased. Material inks were purchased from Sigma Aldrich and cartridges were purchased directly from Dimatix. The budget did not include enough funding to obtain a commercial solar cell tester, which typically cost eight to ten thousand dollars. Glass substrates were used because the cost of heat resistance flexible substrates was not within the project budget. 7 The third material layer P3HT:PCBM was not available to be purchased in ink form. The P3HT and PCBM material was purchased from Ossila. A one-to-one ratio of P3HT:PCBM blend was dissolved in dichlorobenzene to create a 12.5mg/mL ink solution. Dr. Burnett of the chemistry department assisted with the ink synthesis. See Appendix D for detailed ink synthesis instructions. 8 CHAPTER 5. PRINTING PROCESS DEVELOPMENT The print patterns for the multiple material layers were modeled after the patterns outlined in Mitra et al [7]. The Dimatix DMP-2850 materials printer is controlled through the Drop Manager desktop application. Print patterns for each material were originally developed using Adobe Illustrator. The patterns were saved as bitmap files and loaded on to the Dimatix printer computer using a flash drive. The bitmap patterns were imported into the drop manger bitmap pattern editor application and converted to vector point data pattern files. However, there was an issue with the bitmap pattern conversion. The dimensions of the patterns developed in Adobe Illustrator converted to much smaller vector point data patterns. This issue remains unresolved but was not critical to success of the project. Due to the bitmap pattern conversion issue, the print patterns were developed directly in the drop manager pattern editor application. This application allows a pattern to be created out of rectangles. Because the materials layer patterns were easily created by using single or multiple rectangles, utilizing the pattern editor application to create patterns was not an issue. The pattern editor application is not well suited for constructing complex or circular patterns, because the pattern editor restricts pattern development to the use of rectangles. Figure 5.1 illustrates the pattern developed for the PEDOT:PSS layer. 9 Figure 5.1 PEDOT:PSS Printer Set-Up Initial printing parameters and cartridge settings were modeled after the print parameter table from Mitra et al [7]. Jetting waveforms for each material ink were developed using the drop manager waveform editor and modeled after the waveforms depicted in the Mitra et al [7], where Table 5.1 illustrates these various printing parameters. Table 5.1 Printing Parameters from Mitra et al [7] Initial printing parameters were modeled directly from Table 1. However, those printing parameters did not produce clean and precise patterns. The ZnO layer did not print when attempting to use the same printing parameters. As a result, several hours were spent developing new printing parameters and cartridge settings. The drop manager has a drop watcher camera application that allows the user to watch the 10pL droplets leave the printhead while adjusting printing parameters and 10 cartridge settings. The drop watcher application proved to be a very useful tool. Print parameters and cartridge settings were adjusted and the drop watcher was then used to observe how well the material ink was printing. This process was repeated until cartridge settings were developed that produced uniform printing for a particular ink. Test patterns were then printed on a glass substrate and the uniformity of the patterns were observed. Figure 5.2 depicts a test print pattern for the bottom Ag layer. Figure 5.2 Ag Test Pattern New printing parameters and cartridge settings were developed for each material layer. The table below depicts the new printing parameters and cartridge settings used throughout solar cell printing process. Table 5.2 Developed Printing Parameters Functional layer No. of Nozzles Jetting Voltage (V) Substrate Temperature (°C) Cartridge Temperature (°C) Drop Spacing (μm) and No. of Layers Curing Time (°C, min) Ag 16 16 28 28 15 & 2 150, 30 ZnO 16 18 28 36 10 & 4 135, 20 P3HT:PCBM 16 10 60 50 15 & 3 120, 20 PEDOT:PSS 10 16 28 28 6 & 2 70, 15 The developed printing process was implemented to produce functional solar cells. Figure 5.3 depicts a fully printed solar cell fabricated at Weber State University. A total of fourteen solar cells were printed. For more detailed printing process instructions please see Appendix B. 11 Figure 5.3 Fully Printed Solar Cell Example 12 CHAPTER 6. SOLAR CELL TESTING Tests were conducted utilizing the physics department’s testing equipment. Training on the equipment and guidance was provided by the physics department throughout the design project. The solar cell’s performance was evaluated using an ELH light source, Keithley source meter, and IV software on a computer. The Keithley source meter utilized a four-point probe system, which reduces IV sweep error caused by the Schottky effect. The solar cells were exposed to the ELH light source and a voltage-current sweep was performed. Voltage vs current plots were obtained using the IV software. The voltage-current curves depict the solar cell’s open-circuit voltage (Voc) and closed-circuit current (Isc). IV data was imported into Matlab and a script file was developed to find the maximum power for a specific operating point. A polyfit curve was developed to create an IV curve that included thousands of points. This curve was used to find the maximum operating point. The physics department has a calibrated silicon solar cell. This solar cell was tested under the same testing conditions as the printed solar cells. Figure 6.1 illustrates the IV curve obtained for the calibrated cell. The Voc occurs where the IV curve crosses the x axis and the Isc occurs where the IV curve crosses the y axis. The blue shaded rectangle is the maximum power area. This rectangle has the maximum area possible and the right bottom corner of the rectangle corresponds to the maximum operating point. The maximum operating point is a point on the IV curve between Voc and Isc where the corresponding current and voltage yield the greatest power when multiplied together. 13 Figure 6.1 Calibrated Solar Cell IV Curve IV curve data was obtained for five functional solar cells. The plots below illustrate the maximum power, short circuit current, and open circuit voltage of each solar cell. The Matlab IV curves obtained from the printed solar cells are far from textbook IV examples. The appearance of the printed solar cell IV curves most likely due to the relatively poor performance of the printed solar cells. In Figure 6.2, the blue curve depicts a voltage-current sweep that was performed when the ELH light source was turned off. The data1 and data2 curves show that the solar cell device reacts when exposed to the ELH light source and generates a small amount of power. 14 Figure 6.2 IV Curve for a Fully Printed Solar Cell Organic solar cells are known for low power conversion efficiencies. The organic printed solar cells developed by researchers Mitra et al achieved power conversion efficiencies in the 0.02% to 0.18% range, Voc of 400mV, Isc of 43μA, and maximum power of 8.75μW [7]. However, other advantages have made organic solar cells a potential solar energy solution. These advantages include solution processability, reduced cost, and freedom of form. The solar cells are extremely fragile which made testing very difficult. Several cells were damaged while testing. The solar cells were also damaged when exposed to the heat generated by the ELH light source. 15 CHAPTER 7. SOLAR CELL PRINTING AND TESTING CHALLENGES Throughout the printing process several unexpected obstacles were encountered. The first and foremost challenge was developing printing parameters and cartridge settings. The print settings outlined in the research article did not produce clean, even, and precise patterns. There are a number of reasons why these print parameters may not have worked, such as the Dimatix printers are different models, jetting waveforms were not identical because there was not enough detail in the research article to exactly replicate the waveforms, different substrates were used, and the inks were not identical because the article did not include enough information. A glass slide substrate was used instead of the thin flexible substrate used in the research article. As a result, an enormous amount of time was spent developing printing parameters and cartridge settings for each material layer. The Dimatix ink cartridges are one-time use disposable cartridges that become clogged very easily. In general, the cartridges print best right after filling the cartridge with ink. Depending on the ink, after sitting at room temperature for a few days the cartridge would not print when using proven printing parameters. The PEDOT:PSS ink was particularly bad when it came to this issue. The PEDOT:PSS ink cartridge would become clogged very quickly and the cartridge would not print the next day. The DMP- 2850 has three different cleaning settings purge, spit, and blot. The PEDOT:PSS ink became clogged so quickly, a one second purge and blot was run every sixty seconds while printing to ensure the nozzles weren’t clogged. The PEDOT:PSS cartridges were not usable a day after initial printing. Several different cleaning methods were investigated to address this issue. Attempts were made 16 to use 0.45μm syringe filters but PEDOT:PSS ink would not pass through the filter when filling the cartridge. After sitting at room temperature for a day or more, several Dimatix printer cleaning cycles were run and the drop watch was used to observe if any nozzles became unclogged. The cartridges were placed inside plastic bags and put in an ultra-sonic bath for forty-five minutes. The cartridge print heads were cleaned with alcohol and a cloth, this was done to remove visible ink that had dried on the print head. No combination of cleaning methods successfully unclogged the cartridges. As a result, several cartridges were wasted that still have ink in them. It’s important to note that the PEDOT:PSS ink cartridges became clogged much faster than ink cartridges filled with other material inks. Cartridges filled with Ag and ZnO ink were usable for up to three weeks after initial cartridge filling. Cartridges filled with P3HT:PCBM are usable for up to two weeks after initial cartridge filling. All of the material ink cartridges became clogged over time. Only one Ag ink cartridge was used throughout the printing process. Because the printed Ag layer stores well at room temperature and does not degrade over time, it is recommended to print all required Ag patterns at one time. The Ag patterns can be stored and utilized in future solar cell printing batches. Because the ZnO, P3HT:PCBM, and PEDOT:PSS layers do not store well and degrade quicky, it is recommend to only print these layers when intending to print the entire solar cell stack structure over a short period of time. Because the solar cells are only a few micrometers thick they are extremely fragile and can easily be damaged. This made testing the solar cells extremely difficult. The testing probes can easily scratch through the contact layers. To help combat this 17 issue copper tape was put over the Ag contact which extended the contact. The PEDOT:PSS contact was made much larger than the original print pattern which allowed for easier testing. It was observed throughout the printing process that the top PEDOT:PSS layer is extremely sensitive to heat. Three solar cells were damaged during the heating process because the PEDOT:PSS layer began to curl away from the solar cell structure. Due to this issue, the solar cells were heated at a lower temperature for a shorter period of time. Due to the inherent instability of organic solar cells, all of the solar cells degraded over time and eventually stopped functioning because the PEDOT:PSS layer deteriorated. The degradation of the printed solar cells was primarily caused by exposure to heat and air. Organic solar cell stability is a known issue impacting the advancement of solar energy technology. Several factors negatively impact organic solar cell stability such as exposure to air, light, and heat [8]. Researchers are currently investigating methods to preserve and protect these solar cells from degradation [8]. 18 CHAPTER 8. RESULTS AND DISCUSSION The objectives of this project were achieved. A solar cell printing process was developed and used to fabricate functional solar cells. IV data was obtained through testing. The IV data was analyzed using Matlab software and the maximum power operating point was determined. The performance of the solar cells appears poor in comparison to the research article results but the results cannot be directly compared because different testing equipment was used. The calibrated solar cell is a silicon solar cell and was expected to greatly outperform the performance of the organic solar cells. Figures 8.1 through 8.6 depict the IV curve data obtained for five printed solar cells. The solar cell performance characteristics vary greatly among the five printed solar cells. Overall solar cell performance was evaluated based on the maximum power produced. It is important to point out that all of the measured solar cell performance characteristics are relative values because the ELH light source was not calibrated. Solar cell 1 was the best performing printed solar cell with a maximum power of approximately 0.2424nW, Voc of 72mV and, Isc of 12.6nA. See Figure 8.1 below. 19 Figure 8.1 Solar Cell 1 IV Curve With Light On Figure 8.2 depicts the IV curve characteristics of solar cell 1 when the ELH light ELH source was turned off. It’s important to note the overhead lights in the testing lab were still on. The performance characteristics of solar cell 1 decreased greatly when not exposed to the testing ELH light source. Figure 8.2 Solar Cell 1 Light Source Off IV Curve Figure 8.3 depicts the IV curve characteristics of solar cell 2. Because the Isc of solar cell 2 was much smaller than that of solar cell 1, solar cell 2 did not perform as well 20 to solar cell 1 when comparing maximum power. Solar cell 2 had maximum power of approximately 0.08nW, Voc of 62mV and, Isc of 4.9nA. See Figure 8.3 below. Figure 8.3 Solar Cell #2 IV Curve Characteristics Figure 8.4 depicts the IV curve characteristics of solar cell 3. Solar cell 3 had the worst overall performance characteristics of the five printed solar cells. The Voc is relatively large compared to the other solar cells but the Isc is approximately one hundred times smaller than that of solar cell 1. Solar cell 3 had maximum power of approximately 0.45pW, Voc of 104mV and, Isc of 0.013nA. 21 Figure 8.4 Solar Cell #3 IV Curve Characteristics Figure 8.5 depicts the IV curve characteristics of solar cell 4. This IV curve is the most linear IV curve out of the five solar cells and this negatively impacts the maximum power area of the solar cell. Solar cell 4 had maximum power of approximately 0.0215nW, Voc of 83mV and, Isc of 1.7nA. See Figure 8.5 below. Figure 8.5 Solar Cell #4 IV Curve Characteristics Figure 8.6 depicts the IV curve characteristics of solar cell 5. Because the solar cell damaged quickly under the ELH light source, only three IV sweeps were conducted. The PEDOT:PSS layer began to curl away from the device while testing which is why the IV curve appears jagged. Solar cell 5 had maximum power of approximately 22 0.0312nW, Voc of 201mV and, Isc of 0.4nA. See Figure 8.6 below. Solar cell 5 had the largest Voc out of the five printed solar cells. Figure 8.6 Solar Cell #5 IV Curve Characteristics Table 8.1 below summarizes the Voc, Isc, and maximum power for all five printed solar cells. The table also includes the average performance measurements for the five printed solar cells and the maximum power per meter squared. It is clear that a combination of relatively large Isc and Voc values are required to increase the maximum power output. The worst performing solar cell had an Isc in the tens of picoamps range. because the Isc of this solar cell was so much smaller compared to the other printed solar cells, this solar cell also had the worst maximum power performance. Table 8.1 Solar Cell Performance Characteristics Cell No. Isc Voc Maximum Power Maximum Power per Meter Squared (W/m2) Cell 1 12.6 nA 72 mV 0.2424 nW 13.85 μW/m² Cell 2 4.9 nA 62 mV 0.08 nW 4.57μW/m² Cell 3 13 pA 104 mV 0.45 pW 25.7nW/m2 Cell 4 1.7 nA 83 mV 21.5 pW 1.23μW/m² Cell5 0.4 nA 201 mV 31.2 pW 1.78μW/m² Average 3.9 nA 104.4 mV 75pW 4.29μW/m² Cell 1 With ELH Light Source Off 21 pA 1.3 mV 6.71fW 3.8p W/m² NOTE: These solar cell characteristics are based on a device area of 17.5𝑚𝑚􀬶􃘠 23 CHAPTER 9. CONCLUSION AND FUTURE WORK The developed printing process has successfully been utilized to fabricate fully printed solar cells. The evaluation process characterized the open-circuit voltage and short-circuit current of the solar cells when exposed to a specific light source. The fabricated solar cells and IV curve data require further analysis in order to better quantify the solar cells performance characteristics. The developed printing process will serve as a baseline for further solar cell research at Weber State University. IV curve data was obtained for five printed solar cells. The IV curves illustrate that the solar cells produce a small amount of power when exposed to light. The five printed solar cells had a wide range of performance characteristics. The top performing printed solar cell had a maximum power of approximately 0.24nW, Voc of 72mV and, Isc of 12.6nA. The maximum power from the worst performing solar cell was approximately one hundred times smaller than that of the top performing solar cells. The wide range of solar cell performance may be attributed to the inherent instability of solar cells. Many of the challenges encountered throughout the design project involved the PEDOT:PSS anode layer. The PEDOT:PSS layer is difficult to print and unstable when exposed to heat and air. If the solar cell is heated for too long the PEDOT:PSS layer degrades quickly. If the solar cell is not heated for a long enough period of time the PEDOT:PSS layer is not dry enough to function as the anode layer. Because the performance of the solar cells can vary greatly over a short period of time, it is very difficult to know when to test the printed solar cells. A study of how heat and air exposure affect the stability of the printed solar cells, particularly the PEDOT:PSS layer 24 would be very useful. Methods to improve solar cell stability such as encapsulation should be investigated. Moving forward, different material layers should be investigated. Alternative materials with similar electrical properties should be investigated to be utilized in lieu of PEDOT:PSS. This would help with the printing and testing process and could potentially deliver more efficient and repeatable solar cells. More advanced testing equipment is required to fully quantify the solar cell performance characteristics. A light source with a known light spectrum and solar irradiance is needed to determine the power conversion efficiency and fill factor of the solar cells. 25 Bibliography [1] “Best Research-Cell Efficiency Chart,” NREL.gov, www.nrel.gov/pv/ cell-efficiency.html. [2] Bihar, E., Corzo, D., Hidalgo, T. C., Rosas‐Villalva, D., Salama, K. N., Inal, S., Baran, D., “Fully Inkjet‐Printed, Ultrathin and Conformable Organic Photovoltaics as Power Source Based on Cross‐Linked PEDOT:PSS Electrodes,” Adv. Mater. Technol. vol. 5, 2020, p. 2000226, doi: 10.1002/admt.202000226. [3] Jung, S., Sou, A., Banger, K., Ko, Doo-Hyun, Chow, P. C. Y., McNeill, C. R., Sirringhaus, H. “All‐Inkjet‐Printed, All‐Air‐Processed Solar Cells,” Adv. Energy Mater., vol. 4, 2014, p. 1400432. doi: 10.1002/aenm.201400432. [4] C. Chen and C. Yen, "Inkjet Printing of TiO2 Photoelectrodes and Manufacturing of Large-Area Dye-sensitized Solar Cell (DSSC) Modules,” 2018 IEEE 7th World Conference on Photovoltaic Energy Conversion (WCPEC) (A Joint Conference of 45th IEEE PVSC, 28th PVSEC & 34th EU PVSEC), Waikoloa Village, HI, 2018, pp. 1095- 1098. [5] S. Sumaiya, K. Kardel and A. E. Shahat, "Organic solar cell by inkjet printing — An overview," 2017 IEEE SmartWorld, Ubiquitous Intelligence & Computing, Advanced & Trusted Computed, Scalable Computing & Communications, Cloud & Big Data Computing, Internet of People and Smart City Innovation (SmartWorld/SCALCOM/UIC/ATC/CBDCom/IOP/SCI), San Francisco, CA, USA, 2017, pp. 1-8, doi: 10.1109/UIC-ATC.2017.8397439. [6] T.M. Eggenhuisen, Y. Galagan, “Digital fabrication of organic solar cells by Inkjet printing using non-halogenated solvents,” Solar Energy Materials and Solar Cells, vol. 134, 2015, pp. 364-372, doi: 10.1016/j.solmat.2014.12.014. [7] K. Y. Mitra, A. Alalawe, S. Voigt, C. Boeffel, and R. R. Baumann, “Manufacturing of All Inkjet-Printed Organic Photovoltaic Cell Arrays and Evaluating their Suitability for Flexible Electronics,” Micromachines, vol. 9, p. 642, Dec. 2018. [8] Duan, L., Uddin, A., “Progress in Stability of Organic Solar Cells,” Adv. Sci., vol. 7, 2020, p. 1903259. doi: 10.1002/advs.201903259. 26 APPENDIX A. PRINTER TURN ON, PRINT PATTERNS, AND JETTING WAVEFORMS The purpose of Appendix A is to explain how to turn on the Dimatix printer and open the drop manger application, how to use the drop manger pattern editor to create a print pattern from scratch, and how to create and edit jetting waveforms. 27 Turning on the Printer 1) Ensure that the lab computer monitor, mouse, and key board are plugged into the Dimatix printer. 2) Turn on the printer by using the switch on the front right of the printer. 3) Launch the Dimatix drop manger app by clicking the desktop Icon (shown below) 4) Ensure that the printer is not obstructed by making sure there isn’t a substrate in the printer and click OK on the pop up. Steps to Create a pattern 1)In the drop manger home page click on the tools->pattern editor. 28 2) The Following window will be generated 3) the pattern array is the total space of your design or substrate and the drop position array is the actual design area that will be printed. 4) A pattern can be created by manipulating the X and Y parameters to create rectangles. 5) Multiple rectangles can be added to created the required pattern by clicking the add button. The screen shot above shows that the drop pattern consists of three rectangles. 6) the pattern can be observed by clicking preview drops (shown below) 29 7) NOTE: The number of Layers and drop spacing can be manipulated using the layer count tab and the drop spacing tab. Uploading an existing pattern ptn file: 1) If your pattern is on a thumb drive, unplug the keyboard from the printer and insert the thumb drive. 2) Browse to the pattern using file explorer and save the file to the printer. 3) In the Dimatix Drop Manger go to tools->pattern editor-> open-> then browse to the pattern file and open. 4) Your pattern will then be uploaded Creating Jetting Voltage waveform 1) In the dimatix Drop Manger go to tools-> wave form generator (the following window should appear) 2) The wave form can be edited by using the Level, Slew Rate, and Duration. The level is the percentage of jetting voltage. The actual jetting voltage is not set here. The slew rate is the slope of the wave form and the duration is the is the duration of the highlighted waveform segment. 3) Wave form segments can be added or deleted by selecting the add segment or delete segment buttons. The wave form shown above consists of five different segments 30 APPENDIX B. PRINTING PROCESS INSTRUCTIONS The purpose of Appendix B is to provide detailed printing process instructions. These printing instructions will allow Weber State University students and faculty to replicate the developed printing process. The printing instructions will serve as a baseline process for further research. Note: at this point in the design the material layer print patterns and jetting waveforms have already been developed. Please see the Appendix for more information. 31 Contents: Section 1: Printer Start Up Section 2: Printing the 1st Material Layer (Ag) Section 3: Printing the 2nd Material Layer (ZnO) Section 4: Printing the 3rd Material Layer (P2HT:PCBM) Section 5: Printing the 4th Material Layer (PEDOT:PSS) Section 6: Testing Printed Solar Cell 32 Section 1: Printer Start Up Step 1) Turn on the printer by using the switch on the bottom right of the printer [9] Step 2) Drop Manger The printer is controlled by the drop manger desktop application shown below, Select the drop manger icon. 33 Figure 2: Printer Computer Desktop Drop Manger Icon Step 3) initial calibration After clicking the icon, the following pop-up window appears. Ensure that there is nothing in the printer and click okay. The printer will begin initializes. Note: the initialization process takes several seconds. [9] Figure 3: Initial Calibration Pop-Up After initialization completes you should see the following application window 34 Figure 4: Drop Manager Start Screen [9] It is now time to prepare the printing parameters for printing. Section 2: Layer one printing Ag Step 1: Verify the print pattern and jetting waveform 1.1: Go to tools -> select pattern editor 1.2: The pattern editor window opens. 1.3: Select file->open then browse to the Ag file pattern and select file Agtest.pnt 1.4: Verify that the drop spacing is set at 15um and the layer count is 2. (check off here) 1.5: close the pattern editor window and move to the next step Step 2) Replace Cleaning Pad 35 2.1: Remove the plastic cleaning pad cover from the new cleaning pad. 2.2: Use the plastic cover to extract the old cleaning pad by pushing it down until it clicks over the cleaning pad. Then pull up on the plastic cap to extract the old cleaning pad. 2.3 Push the new cleaning pad into the cleaning pad holder until it clicks. (as illustrated below) Figure 5: Replace Cleaning Pad [9] Step 3) Fill Dimatix Cartridge with Ag ink 3.1: Using a syringe withdraw 4.5mL of ink from bottle. 3.2: Remove needle form syringe and place filter on end of syringe. 3.3: Put the needle back on syringe. 3.4: Inject the ink directly into the Dimatix ink cartridge reservoir. 3.5: Clip the reservoir into the Dimatix ink head. 3.6: Label cartridge for particular ink Step 4) Load ink cartridge into printer 4.1: Select the install ink cartridge tab. 36 Figure 6: Installing Ink Cartridge Drop Manger Page[9] 4.2: Lift up the ink cartridge holder as shown below. Figure 7: Ink Cartridge Holder [9] 4.3: Insert the ink cartridge into the cartridge holder. The cartridge only fits in one way. Ensure that the cartridge clicks in. 37 Figure 8: Loading Ink Cartridge [9] 4.4: Once the ink cartridge has been loaded close the cartridge holder back down. The holder should click into place. Figure 9: Installed Cartridge with Ink Holder Closed[9] 4.5: Close the lid to the printer. The following pop-window should appear. Select no and move to the following step. 38 Step 5) Cartridge Settings (This is where the jetting voltage, number of nozzles, cartridge temperature, and jetting waveform are selected) 5.1: upon selecting no in the previous step the following cartridge settings window should have appeared. 5.2: Select the select button and browse the cartridge settings file named newAg. This cartridge settings file has been developed specifically for printing the Ag layer. All of the developed settings are saved in this file. Step 6) Select Pattern Tab 6.1: After saving the cartridge settings you should automatically be at the select pattern tab 6.2: Click the select button under print pattern. 6.3: Browse to the AgTest pattern and select the pattern 39 6.4: Ensure that the correct pattern is shown under print patterns and select next. Step 7) load/unload substrate 7.1: You should now see a window similar to the one shown below: 7.2: open the printer and load the substrate. Line the substrate up with the origin marker in the upper left corner. For example, if printing on a square glass substrate, two sides of the square should line up with the markings on the perimeter of the printing platform. 7.3: the upper left corner is the default origin make sure later on that the print preview shows that this is the case (see print set-up below) 7.4: The desired Ag print pattern should still be shown under Print Pattern: 7.5: Set the substrate thickness to 2500um (2.5mm) (check off) 7.6: Set the substrate temperature to 28 degrees C (check off) 7.7: Set the vacuum to On (check off) 7.8: Ensure that the load/unload substrate window looks correct and click next. 40 Step 8) Print Set-Up 8.1: you should now see the print set-up window similar to the one shown below: 8.2: Ensure that the correct settings are shown: 8.2.1: Print Pattern is the AgTest print pattern (check off) 8.2.2: Substrate settings: 2500um thick, 28 degrees, and vacuum on (check off) 8.2.3: Cartridge settings should show the Ag solar cell settings previously saved. 8.2.4: If all parameters look correct. Select file and ensure that print preview is enabled. 41 8.3: Select the green print button in the bottom right corner. A Print preview screen should pop-up similar the example shown below Figure: Example of Print Preview Window [9] 8.4: If the origin/print preview looks correct select the print button to begin printing. Step 9) Heating the Printed Device 9.1: The printed design must be printed to remove any remain solvent 9.2: Turn on hot plate and set the temperature to 150 degrees C (check) 9.3: Once the hot plate reaches the correct temperature remove the substrate from printer using semiconductor tweezers. 42 9.4: immediately start a timer for 30 minutes. After 30 minutes remove the device from the hot plate. Place device on clean heat resistant surface Step 10) Repeat steps 6 through 9 until the you done printing the silver layer. Once empty remove the cartridge by opening the cartridge holder and then pulling up on the cartridge. Close the holder once the cartridge has been removed. 43 Section 3: 2nd Layer printing ZnO Step 1: Verify the print pattern and jetting waveform 1.1: Go to tools -> select pattern editor 1.2: The pattern editor window opens 1.3: Select file->open then browse to and open the ZnOTest.ptn file pattern 1.4: verify that the drop spacing is set at 10um and the layer count is 4. (check off here) 1.5: close the pattern editor window and move to the next step Step 2) Replace Cleaning Pad 2.1: As done in Section 2 step 2. Step 3) Fill Dimatix Cartridge with ZnO ink 3.1: As done in Section 2 step 3 Step 4) Load ink cartridge into printer 4.1: As done in section 2 step 4. Step 5) Cartridge Settings (This is where the jetting voltage, number of nozzles, cartridge temperature, and jetting waveform are selected) 5.1: upon selecting no in the previous step the following cartridge settings window should have appeared. 5.2: Select the select button and browse the cartridge settings file named ZnO Dan Philpot. This cartridge settings file has been developed specifically for printing the ZnO layer. All of the developed settings are saved in this file. Step 6) Select Pattern Tab 6.1: After saving the cartridge settings you should automatically be at the select pattern tab 6.2: Click the select button under print pattern. 44 6.3: Browse to the ZnOTest pattern file location and select the pattern 6.4: Ensure that the correct pattern is shown under print patterns and select next. Step 7) load/unload substrate 7.1: open the printer and load the substrate in accordance with section 2 step 6. Line the substrate up with the origin marker in the upper left corner. NOTE: this substrate has already had the 1st material layer Ag printed on it. 7.2: the upper left corner is the default origin make sure later on the print preview shows that the origin has not changed. NOTE: Make sure that the substrate is loaded in the same orientation that it was previously 7.3: The desired ZnO print pattern should still be shown under Print Pattern: 7.4: Set the substrate thickness to 2200um (2.2mm) (check off) 7.5: Set the substrate temperature to 28 degrees C (check off) 7.6: Set the vacuum to On (check off) 7.7: Ensure that the load/unload substrate window looks correct and click next. 45 Step 8) Print Set-Up 8.1: you should now see the print set-up window similar to the one shown below: 8.2: Ensure that the correct settings are shown: 8.2.1: Print Pattern is the ZnO print pattern (check off) 8.2.2: Substrate settings: 2200um thick, 28 degrees, and vacuum on (check off) 8.2.3: Cartridge settings should show the ZnO Dan Philpot solar cell settings previously saved. 8.2.4: If all parameters look correct. Select file and ensure that print preview is enabled. 8.3: Select the green print button in the bottom right corner. A Print preview screen should pop-up similar the example shown below 8.4: If the origin/print preview looks correct select the print button to begin printing. 46 Step 9) Heating the Printed Device 9.1: The printed design must be printed to remove any remain solvent 9.2: Turn on hot plate and set the temperature to 135 degrees C (check) 9.3: Once the hot plate reaches the correct temperature remove the substrate from printer using semiconductor tweezers. 9.4: immediately start a timer for 20 minutes. After 20 minutes remove the device from the hot plate. Place device on clean heat resistant surface Step 10) Repeat steps 6 through 9 until done printing the ZnO layers. 10.1: Once empty remove the cartridge by opening the cartridge holder and then pulling up on the cartridge. 10.2: Close the holder once the cartridge has been removed. 47 Section 4: 3nd Layer printing P3HT:PCBM Step 1: Verify the print pattern and jetting waveform 1.1: Go to tools -> select pattern editor 1.2: The pattern editor window opens. 1.3: Select file->open then browse and open to the P3HT:PCBMtest file pattern 1.4: verify that the pattern editor window is identical to the one shown below. Also make sure that the drop spacing is set at 15um and the layer count is 3. (check off here) 1.5: close the pattern editor window and move to the next step Step 2) Replace Cleaning Pad 2.1: As done in Section 2 step 2. Step 3) Fill Dimatix Cartridge with P3HT:PCBM ink 3.1: As done in Section 2 step 3 Step 4) Load ink cartridge into printer 4.1: As done in section 2 step 4. Step 5) Cartridge Settings (This is where the jetting voltage, number of nozzles, cartridge temperature, and jetting waveform are selected) 5.1: upon selecting no in the previous step the following cartridge settings window should have appeared. 5.2: Select the select button and browse the cartridge settings file named P3HT:PCBM 2nd Cart. This cartridge settings file has been developed specifically for printing the P3HT:PCBM layer. All of the developed settings are saved in this file. 5.3: In the Cartridge Settings window go to file then select save to save the settings. Then close the window 48 Step 6) Select Pattern Tab 6.1: After saving the cartridge settings you should automatically be at the select pattern tab 6.2: Click the select button under print pattern. 6.3: Browse to the P3HT:PCBMtest pattern file location and select the pattern 6.4: Ensure that the correct pattern is shown under print patterns and select next. Step 7) load/unload substrate 7.1: open the printer and load the substrate in accordance with section 2 step 6. Line the substrate up with the origin marker in the upper left corner. NOTE: this substrate has already had the 1st and 2nd material layers Ag and ZnO printed on it. 7.2: the upper left corner is the default origin make sure later on the print preview shows that this is the case (see print set-up below) NOTE: Make sure that the substrate is loaded in the same orientation that it was previously 7.3: The desired P3HT:PCBM print pattern should still be shown under Print Pattern: 7.4: Set the substrate thickness to 2200um (2.2mm) (check off) 7.5: Set the substrate temperature to 60 degrees C (check off) 7.6: Set the vacuum to On (check off) 7.7: Ensure that the load/unload substrate window looks correct and click next. Step 8) Print Set-Up 8.1: you should now see the print set-up window similar to the one shown below: 49 8.2: Ensure that the correct settings are shown: 8.2.1: Print Pattern is the P3HT:PCBM 2nd Cart print pattern (check off) 8.2.2: Substrate settings: 2200um thick, 60 degrees, and vacuum on (check off) 8.2.3: Cartridge settings should show the P3HT:PCBM 2nd Cart solar cell settings previously saved. 8.2.4: If all parameters look correct. Select file and ensure that print preview is enabled. 8.3: Select the green print button in the bottom right corner. A Print preview screen should pop-up similar the example shown below 8.4: If the origin/print preview looks correct select the print button to begin printing. 50 Step 9) Heating the Printed Device 9.1: The printed design must be printed to remove any remain solvent 9.2: Turn on hot plate and set the temperature to 120 degrees C (check) 9.3: Once the hot plate reaches the correct temperature remove the substrate from printer using semiconductor tweezers. 9.4: immediately start a timer for 20 minutes. After 20 minutes remove the device from the hot plate. Place device on clean heat resistant surface Step 10) Repeat steps 6 through 9 until done printing the P3HT:PCBM layers. 10.1: Once empty remove the cartridge by opening the cartridge holder and then pulling up on the cartridge. 10.2: Close the holder once the cartridge has been removed. NOTE: The printing platform takes over an hour to cool back down to room temperature. Turn the substrate temperature down before leaving the lab. 51 Section 5: 4th Layer printing PEDOT:PSS NOTE: the PEDOT:PSS layer does not print easily it may be necessary to print extra layers where the solar cell borders the glass. See picture below: Step 1: Verify the print pattern and jetting waveform 1.1: Go to tools -> select pattern editor 1.2: The pattern editor window opens. 1.3: Select file->open then browse to and open the PEDOT:PSS test num 2 file pattern 1.4: verify that the pattern editor window is identical to the one shown below. Also make sure that the drop spacing is set at 6um and the layer count is 2. (check off here) 1.5: close the pattern editor window and move to the next step 52 Step 2) Replace Cleaning Pad 2.1: As done in Section 2 step 2. Step 3) Fill Dimatix Cartridge with PDOT:PSS ink 3.1: As done in Section 2 step 3 Step 4) Load ink cartridge into printer 4.1: As done in section 2 step 4. Step 5) Cartridge Settings (This is where the jetting voltage, number of nozzles, cartridge temperature, and jetting waveform are selected) 5.1: upon selecting no in the previous step the following cartridge settings window should have appeared. 5.2: Select the select button and browse the cartridge settings file named PEDOT:PSS Final Test. This cartridge settings file has been developed specifically for printing the PEDOT:PSS layer. All of the developed settings are saved in this file. Step 6) Select Pattern Tab 6.1: After saving the cartridge settings you should automatically be at the select pattern tab. 6.2: Click the select button under print pattern. 6.3: Browse to the PEDOT:PSS test num 2 pattern file location and select the pattern 6.4: Ensure that the correct pattern is shown under print patterns and select next. Step 7) load/unload substrate 7.1: open the printer and load the substrate in accordance with section 2 step 6. Line the substrate up with the origin marker in the upper left corner. NOTE: this substrate has already had the 1st , 2nd , and 3rd material layers Ag, ZnO, and P3HT:PCBM printed on it. 7.2: the upper left corner is the default origin make sure later on the print preview shows that this is the case (see print set-up below) 53 NOTE: Make sure that the substrate is loaded in the same orientation that it was previously. 7.3: The desired PEDOT:PSS print pattern should still be shown under Print Pattern: 7.4: Set the substrate thickness to 2200um (2.5mm) (check off) 7.5: Set the substrate temperature to 28 degrees C (check off) 7.6: Set the vacuum to On (check off) 7.7: Ensure that the load/unload substrate window looks correct and click next. Step 8) Print Set-Up 8.1: you should now see the print set-up window similar to the one shown below: 8.2: Ensure that the correct settings are shown: 8.2.1: Print Pattern is the PEDOT:PSS test num 2 print pattern 54 (check off) 8.2.2: Substrate settings: 2200um thick, 28 degrees, and vacuum on (check off) 8.2.3: Cartridge settings should show the PEDOT:PSS final test solar cell settings previously saved. 8.2.4: If all parameters look correct. Select file and ensure that print preview is enabled. 8.3: Select the green print button in the bottom right corner. A Print preview screen should pop-up similar the example shown below 8.4: If the origin/print preview looks correct select the print button to begin printing. Step 10) Heating the Printed Device 10.1: The printed design must be printed to remove any remain solvent 10.2: Turn on hot plate and set the temperature to 70 degrees C (check) 10.3: Once the hot plate reaches the correct temperature remove the substrate from printer using semiconductor tweezers. 10.4: immediately start a timer for 15 minutes. After 15 minutes remove the device from the hot plate. Place device on clean heat resistant surface Step 11) Repeat steps 6 through 9 until the dimatix ink cartridge is empty. 11.1: Once empty remove the cartridge by opening the cartridge holder and then pulling up on the cartridge. 10.1: Close the holder once the cartridge has been removed. Reference[9]: Dimatix_SOP (upenn.edu) 55 APPENDIX C. MATLAB IV SCRIPT The purpose of Appendix C is to show an example of a Matlab script that was used to generate IV plots. Note that the IV curve data was saved off of the IV software and imported into Matlab. The imported data was copied and pasted into the Matlab script. A polyfit curve was used to model the IV data. The IV curve was used to find the Voc, Isc, and maximum power values. 56 clear cell6VoltageV2= Copy and past IV Voltage Data here cell6CurrentA2= Copy and past IV Current Data here p=polyfit(cell6VoltageV2,cell6CurrentA2,10000); f = polyval(p,cell6VoltageV2); T = table(cell6VoltageV2,cell6CurrentA2,f,cell6CurrentA2- f,'VariableNames',{'X','Y','Fit','FitError'}); S=[-0.8:0.0001:0.8]; F=polyval(p,S); ns=16001; %multiply corresponding currents and voltages for is=1:ns if (S(is)> 0 && F(is)<0) wer(is)=S(is).*F(is); else wer(is)= 0; end end Pm=wer; %Find Max Power [M,max_idx]=max(abs(Pm(:))) Pcurrentmax=F(max_idx) Pvoltagemax=S(max_idx) Pcheck=Pcurrentmax*Pvoltagemax; %Find Isc [mi,mi_idx]=min(abs(S(:))) Isc=F(mi_idx) %find Voc [mv,mv_idx]=min(abs(F(:))) Voc=S(mv_idx) PsqV=[-1:0.001:1]; PsqI1 = zeros(1,length(PsqV)); %Generate Plots figure hold on %power area rectangle patch([0 Pvoltagemax Pvoltagemax 0], [Pcurrentmax Pcurrentmax 0 0],'b','DisplayName','Power Area') plot(PsqV,PsqI1,'k','Linewidth',1.5) plot(PsqI1,-PsqV,'k','Linewidth',1.5) % plot(VoltageV4,f,'x') 57 plot(cell6VoltageV2,cell6CurrentA2,'DisplayName','Orignial I-V data')%orginal I-V curve data plot(S,F,'-','DisplayName','PolyFit data') plot(0,Isc,'o','DisplayName','Isc=146mAmps') plot(Voc,0,'o','DisplayName','Voc=568mVolts') %plot(S,Pm) plot(Pvoltagemax,Pcurrentmax,'o','DisplayName','Max Power Point 53mWatts') title('Calibrated Solar Cell I-V Curve') hold off legend('show') title(legend,'Calibrated Solar Cell I-V Curve') ylabel('Current (Amps)') xlabel('Voltage (Volts)') grid on %axis([-0.05 0.17 -0.00000003 0.00000002]) axis([-0.7 1 -0.160 0.10 ]) 58 APPENDIX D. INK SYNTHESES The purpose of Appendix D is to provide step by step instructions for making 5mL of the P3HT:PCBM donor acceptor blend ink. These instructions include information on how to measure the correct amounts of P3HT and PCBM, add dichlorobenzene to the dry material, and dissolve the dry material using an ultra-sonic bath. 59 Step 1: Weighing dry P3HT and PCBM Material 1.1 Take a square piece of wax paper (approximately 2inches by 2inches) then place the paper on the electronic scale and push the zero button to calibrate the scale back to zero. 1.2 Open the P3HT container and deposit 31.25mg of P3HT material onto the wax paper using a narrow metal micro spatula. NOTE: Deposit small amounts of material at a time to ensure that too much material is deposited on the wax paper. 1.3 Once the electronic scale reads 31.25mg of material carefully use the wax paper as funnel and deposit the material into a glass vile. 1.4 Repeat Step one for the PCBM material. Step 2: Depositing Dichlorobenzene into the Vial 2.1 Set a calibrated pipette similar to the one shown in the figure below to 1mL by adjusting the volume knob. 60 2.2 Open the bottle of dichlorobenzene under an air-controlled chemistry lab hood. 2.3 Push down on the pipette top push button until it stops. Then insert the pipette tip into the dichlorobenzene and release the push button. 2.4 Insert the pipette tip into the vial containing P3HT:PCBM and push down on the top push button. 2.5 Repeat steps 2.3 and 2.4 four more times. Step 3: Using an ultra-sonic bath to dissolve any remaining dry material 3.1 Add water to the ultra-sonic bath reservoir. 3.2 Turn on the sonicator by turning the control knob to 10. 3.3 Make sure the vile containing the ink mixture has been tightly sealed. 3.4 Hold the ink mixture in the water reservoir. Move the vile around until you feel a strong vibration. 61 3.5 Observe the ink solution and repeat step 3.4 until no dry material is observed in the ink solution. Note: Step 3 should only take a few minute 62