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Challenges and Opportunities for Improving Thin-Film Photovoltaics Inna Kozinsky1, Brion Bob2, Rebecca Jones-Albertus3 1 Allegheny Science and Technology, Contractor to DOE, Washington, D.C. 20024 2 DOE SunShot Fellow, Oak Ridge Institute for Science and Education, Oak Ridge, TN 37831 3 SunShot Initiative, U.S. Department of Energy, Washington, D.C. 20024 ABSTRACT The U.S. Department of Energy (DOE)’s SunShot Initiative is a collaborative national effort to reduce the price of solar energy to 6¢/kWh without subsidy for utility scale installations by 2020. Thin-film photovoltaics offer a promising path to reach this goal. Analysis of the levelized cost of energy (LCOE) from photovoltaics (PV) highlights the dependence on the module and system efficiency and lifetime in addition to module price. Here we summarize challenges and opportunities for CdTe and CIGS PV research and show that a substantial effort is still needed in areas such as device design and material improvement to reach higher efficiency and reliability connected with low-cost and robust module-scale implementation. We also discuss how SunShot Initiative funding is addressing key research areas in CdTe and CIGS PV and show how recent progress in SunShot projects is guiding funding priorities in thin-film PV research. INTRODUCTION The U.S. Department of Energy (DOE)’s SunShot Initiative was established in 2011 as a collaborative national effort to make the levelized cost of energy (LCOE) from photovoltaic (PV) systems competitive with conventional electricity sources. The 2020 SunShot goal [1] is 6¢/kWh for utility scale installations without subsidy in locations with moderate sunlight. Further as the penetration of PV on the electric grid increases, the price of PV must continue to fall below these targets to remain competitive, due to challenges related to grid integration and the intermittency of PV. In 2015, the LCOE was benchmarked at 10¢/kWh for utility-scale systems in Kansas City, Missouri, a location with only a moderate solar resource [2]. Further cost reduction to the 2020 SunShot goal and beyond is needed to enable even higher capacity through the reduction in module price, improvement in module efficiency, module reliability, reduction of hardware and labor costs, and lowering of financing costs [2]. Thin-film photovoltaics based on cadmium telluride (CdTe) and copper indium gallium selenide or sulfide (CIGS) amount to ~9% of the total annual worldwide PV production and carry a promise to meet the SunShot goals by offering a low module price with increasing efficiency and reliability. The path to increase thin-film PV module efficiency lies through consistently improving the cell performance and shrinking the gap between cell and module efficiencies. Establishing a low degradation rate (e.g., the SunShot 2020 target of 0.2% per year [2]) and demonstrating module lifetimes of 25-30 years are especially critical for thin-film PV technology due to the comparatively short and sparse record of in-field energy output and insufficient record and un