Efficient electron extraction of SnO2 electron transport layer for lead halide perovskite solar cell

SnO 2 electron transport layer (ETL) has been spotlighted with its excellent electron extraction and stability over TiO 2 ETL for perovskite solar cells (PSCs), rapidly approaching the highest power conversion efficiency. Thus, how to boost the performance of ETL is of utmost importance and of urgent need in developing more efficient PSCs. Here we elucidate the atomistic origin of efficient electron extraction and long stability of SnO 2 -based PSCs through the analysis of band alignment, carrier injection, and interfacial defects in the SnO 2 /MAPbI 3 (MA = CH 3 NH 3 + ) interface using unprecedentedly high level of first-principles calculations at the PBE0 + spin-orbit-coupling + dispersion-correction level for all possible terminations and MA directions. We find that Sn- s orbital plays a crucial role in carrier injection and defect tolerance. SnO 2 /MAPbI 3 shows favorable conduction band alignments at both MAI- and PbI 2 -terminations, which makes the solar cell performance of SnO 2 /MAPbI 3 excel that of TiO 2 /MAPbI 3 . Different electron transfer mechanisms of dipole interaction and orbital hybridization at the MAI- and PbI 2 -terminations indicate that post-transition metal ( sp valence) oxide ETLs would outperform transition metal ( d valence) oxide ETLs for PSCs.