Influence of a UV-ozone treatment on amorphous SnO2 electron selective layers for highly efficient planar MAPbI3 perovskite solar cells

The effect of ultraviolet-ozone (UVO) irradiation on amorphous (am) SnO2 and its impact on the photoconversion efficiency of MAPbI(3)-based perovskite solar cells were investigated in detail. UVO treatment was found to increase the amount of chemisorbed oxygen on the am-SnO2 surface, reducing the surface energy and contact angle. Physicochemical changes in the am-SnO2 surface lowered the Gibbs free energy for the densification of perovskite films and facilitated the formation of homogeneous perovskite grains. In addition, the Fermi energy of the UVO-treated am-SnO2 shifted upwards to achieve an ideal band offset for MAPbI(3), which was verified by theoretical calculations based on the density functional theory. We achieved a champion efficiency of 19.01 % with a statistical reproducibility of 17.01 +/- 1.34 % owing to improved perovskite film densification and enhanced charge transport/extraction, which is considerably higher than the 13.78 +/- 2.15 % of the counterpart. Furthermore, UVO-treated, am-SnO2-based devices showed improved stability and less hysteresis, which is encouraging for the future application of up-scaled perovskite solar cells. (C) 2020 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.