Significantly Enhanced V-oc and Efficiency in Perovskite Solar Cells through Composition Adjustment of SnS2 Electron Transport Layers

The energy level alignment (ELA) between electron transport layers (ETLs) and perovskite layers would affect the photovoltaic performance of perovskite solar cells (PSCs), especially for the open-circuit voltage (V-oc). However, systematic investigations were rarely reported. In this letter, a series of SnS2/SnS composite ETLs were in situ synthesized, where the doping of SnS was used to adjust the energy level of SnS2 nanosheets. Results showed that electrons could be transferred from perovskite layers to ETLs; even the conduction band (CB) of ETLs was a little higher than that of perovskite layers. In comparison with PSCs based on SnS2 ETLs, the power conversion efficiency (PCE) of PSCs based on SnS2/SnS was enhanced by 27.95% (from 14.13% to 18.08%) with a higher V-oc promotion (from 0.94 to 1.08 V). A corresponding explanation and working principle have been proposed. In addition, a stability test demonstrated that PSCs based on SnS2/SnS ETLs possessed much better stability than that of traditional PSCs based on TiO2 ETLs because of the strong interaction of Pb and S. This work proposes a promising future for reducing the V-oc loss and improving the stability of perovskites.