High efficiency solution processed sintered CdTe nanocrystal solar cells: The role of interfaces

Solution processing of photovoltaic semiconducting layers offers the potential for drastic cost reduction through improved materials utilization and high device throughput. One compelling solution-based processing strategy utilizes semiconductor layers produced by sintering nanocrystals into large-grain semiconductors at relatively low temperatures. Using n-ZnO/p-CdTe as a model system, we fabricate sintered CdTe nanocrystal solar cells processed at 350 C with power conversion efficiencies (PCE) as high as 12.3%. J_SC of over 25 mA cm^-2 are achieved, which are comparable or higher than those achieved using traditional, close-space sublimated CdTe. We find that the V_OC can be substantially increased by applying forward bias for short periods of time. Capacitance measurements as well as intensity- and temperature-dependent analysis indicate that the increased V_OC is likely due to relaxation of an energetic barrier at the ITO/CdTe interface.