EAPSI: Increasing energy capture in solar cells made using solar inks

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A dramatic reduction in the cost of flexible, lightweight solar cells (photovoltaics) is needed for direct integration of solar cells with buildings, vehicles, and textiles to be commercially viable. Current solar cell fabrication methods utilize complex, high vacuum processing not readily compatible with flexible materials. Solar paints formulated from Copper Indium Gallium Selenide (CIGS) nanocrystals can be sprayed on most materials to create solar cells, offering a possible route to low cost photovoltaics. However, these devices convert a smaller percentage of the sunlight to electricity than needed for commercial viability. In collaboration with Dr. Lydia Wong of Nanyang Technological University (NTU), this project will investigate how to increase solar cell efficiency by forming a connected CIGS film by heating of the nanocrystals and selenium powder. The specialized equipment available at NTU will allow these experiments to be conducted.Increased power conversion efficiency (PCE) in CIGS nanocrystal photovoltaics has been demonstrated by sintering the nanocrystal film in a selenium environment. Sintering of the nanocrystal grains increases the efficiency of the solar cell, but greater understanding is needed of the role of selenium in the growth process and device performance. Selenium partial pressure is difficult to control, but has significant impact on final film morphology and device performance. This study will systematically investigate the influence of selenium partial pressure on the sintered film characteristics and device PCE using a multizone furnace designed for CIGS photovoltaic fabrication. The proposed activity will explore the factors that increase the efficiency of CIGS nanocrystal photovoltaics as a path to developing ultra-low cost solar cells to fill the unmet need for flexible, light-weight solar power. This NSF EAPSI award is funded in collaboration with the National Research Foundation of Singapore.