Hypervalent potassium xanthate modified SnO2 for highly efficient perovskite solar modules

Tin oxide (SnO2) has been demonstrated as a promising electron transport material for high efficiency perovskite solar cells (PSCs) that made entirely via solution processing at low temperature (<200 °C). However, non-radiative recombination at SnO2|perovskite interface lead to a large voltage loss and performance variation. Herein, we present a facile and effective method to simultaneously reduce the interfacial defects and enhance the charge transfer via modification of SnO2 by hypervalent potassium xanthate. The presence of Lewis acidic centers of the sulfur ligands, gives rise to a strong hypervalent interactions with both Pb2+ on the perovskite and Sn4+ on the SnO2 surface, which accelerates the interfacial charge transfer and suppresses the recombination reaction. As a result, solar cells with a power conversion efficiency (PCE) of 23.4 % with negligible hysteresis are fabricated in light of significantly increased voltage in comparison with the relevant control. Moreover, a stabilized efficiency of 18.8 % for large-area (active area: 48.0 cm2) perovskite solar modules is achieved. The modules retain 90 % of their initial performance after aging at ambient for 600 h, which is substantially improved in comparison with the modules based on pristine SnO2.