Study of the Film and Junction Properties in CIGS Solar Cells Robert Vittoe1 and Tung Ho 2 (Mangilal Agarwal3, Sudhir Shrestha3, and Kody Varahramyan3) Integrated Nanosystems Development Institute (INDI) Indiana University–Purdue University Indianapolis (IUPUI), Indianapolis, IN 46202 1Department of Physics, Purdue School of Science, Indiana University-Purdue University Indianapolis (IUPUI), Indianapolis, IN 46202 2Department of Chemistry, Purdue School of Science, Indiana University-Purdue University Indianapolis (IUPUI), Indianapolis, IN 46202 3Department of Electrical and Computer Engineering, Purdue School of Engineering and Technology, Indiana University-Purdue University Indianapolis (IUPUI), Indianapolis, IN 46202 Abstract Review of Literature Current Status of Research Flexible thin film solar cells are considered the new generation in solar cell technology. Copper Indium Gallium Selenide (CIGS) solar cells have been highly regarded for cost-competitive energy production. The objective of this research is to synthesize CIGS nanoparticles and fabricate solar cells using cost-effective methods such as layer-by-layer (LbL) nanoassembly, spraying deposition and chemical bath deposition. 2005 National Renewable Energy Laboratory (NREL) study states that “high efficiency CIGS solar cells can be fabricated up to a band gap of about 1.2 eV.” (1) The paper also states they achieved Voc of 650-660 mV, current density of 32-33 mA cm-2, fill factor of 77-78% and the best conversion efficiency of 16.5% . (1) 2009 NREL paper states that several of the properties of the CIGS may change from one film to the next and are expected to affect device performance.(2) CIGS solar cell devices were successfully fabricated in our lab and tested by our team. CdS layer was successfully deposited at a thickness of approximately 300 nm, but was observed to be rough which requires further improvement Initial solar cell devices measurements; short circuit current (Isc) of 3x10-8 A and open circuit voltage (Voc) of 0.2 V. Methods to improve the solar cells are currently being researched which include: Selenization, sulfurization of the CIGS layer, and optimizing band gap by switching from CdS buffer layer (2.4 eV) to ZnS (3.7 eV). Results to be presented in the future ZnO CdS CIGS Methods Molybdenum Glass Fabrication of CIGS solar cells using: Multi-step heating of CuCl, InCl3, Se, and GaCl3 in oleyamine to make CIGS nanoparticles Particles were purified by ethanol and chloroform Particles separated in 3 Grades by centrifugation, grade 1 size: 40 nm to 118 nm, grade 2: , and grade 3 UV-VIS-NIR spectroscopy were performed to confirm the absorbance properties of the particles Nanoparticles dispersed in poly(sodium-4-styrenesulfonate) (PSS) for layer-by-layer deposition along with polyethyenimine (PEI) Spray Deposition: Sprayed on the Molybdenum coated substrate with the solution of CIGS in ethanol Chemical Bath Deposition: Dipped the samples inside the mixture of 40mL water, 0.75gr Thiourea, 2.5mL Ammonium Hydroxide and 0.17gr Cadmium Sulfate Analysis of CIGS Solar Cells were performed using: Atomic Force Microscopy (AFM) Keithley 4200 Semiconductor Characterization Micromanipulator Probing Station Structure of a typical CIGS solar cell Introduction Working toward creating sustainable energy source New generation flexible thin film solar cell technology Copper Indium Gallium Selenide (CIGS) to reduce solar cell fabrication costs per kilowatt Compete with current power production technology Our team using various cost effective methods CIGS solar cells have potential to be a cost efficient alternative to silicon based solar cells Use of CIGS nanoparticles allows for construction of a thinner device than with bulk material Fabrication of CIGS solar cells on flexible substrates will broaden range of applications of solar cell devices Size of CIGS nanoparticles in chloroform Atomic Force Microscopy image & graph of a scratch in surface of CdS used to measure thickness of sample References and Acknowledgments K. Ramanathan, J. Keane, and R. Noufi. “Properties of High-Efficiency CIGS Thin-Film Solar Cells”. 31st IEEE Photovoltaics Specialists Conference and Exhibition. February 2005. June 8, 2012. I.Repins, S. Glynn, J. Duenow, T.J. Coutts, W. Metzger, and M.A. Contreras. “Required Materials Properties for High-Efficiency CIGS Modules”. Society of Photographic Instrumentation Engineers (SPIE) 2009 Solar Energy + Technology Conference. July 2009. June 7, 2012. Images courtesy of University of Texas El Paso http://wwwold.ece.utep.edu/research/webedl/cdte/Fabrication/index.htm Special thanks to Parvin Ghane for all her guidance through out this research project and to Dan Minner for his time spent training all of us on the usage of the Atomic Force Microscopy device. This study was sponsored by the Indiana University‐Purdue University Indianapolis (IUPUI) Undergraduate Research Opportunities Program (UROP) and supported by Integrated Nanosystems Development Institute (INDI). Zeta-potential of PEI in water Spray deposition CIGS sample under the hood Sonication of CIGS samples Solar Cell on Probing Station Atomic Force Microscopy