Highly Efficient Perovskite Solar Cells and Their Ultimate Potential

Associate Prof Hideo Ohkita and his collaborators at Kyoto University have succeeded in developing perovskite solar cells with different grain sizes of CH₃NH₃PbI₃ crystals, which exhibit a high power conversion efficiency of more than 19% and small hysteresis. By analyzing the photovoltaic properties in details, they found that the photocurrent generation efficiency is almost 100% for all the grain sizes and that the open-circuit voltage (Voc) increases because of the less trap-assisted recombination in the larger gain sizes. If the trap density were reduced to less than 10¹³ cm^-3 as reported for single crystalline perovskites, the Voc would be further improved to ~1.27 V, which is close to the theoretical limit. Our finding suggests that CH₃NH₃PbI₃ perovskite solar cells have potential to exhibit the theoretical limit voltage as well as the 100% efficient photocurrent generation.