Dip-Coated SnO2 Electron Transport Layer for Efficient and Stable PbS Quantum Dot Photovoltaics

Advance in wide-bandgap-oxide electron transport layers (WBO-ETLs) is essential for the development of high-efficiency and stable solution-processed quantum dot photovoltaics (PVs). Herein, a novel dip-coated SnO2 ETL to fabricate PbS colloidal quantum dot solar cells (CQDSCs) is employed, replacing the benchmarked ZnO sol-gel ETL, in pursuit of both high efficiency and high operational stability. Taking advantage of the high light-transmittance and desired electrical characteristics of the dip-coated SnO2 ETL, the CQDSC with a structure of fluorine-doped tin oxide (FTO)/SnO2/1-capped PbS CQDs/EDT-capped PbS/Au (EDT: 1,2-ethanedithiol), exhibits a champion power conversion efficiency (PCE) of 10.70%, higher than the 9.52% of the ZnO-based control device. Particularly, the unencapsulated SnO2-based CQDSC demonstrated a remarkably improved operational stability in comparison to the ZnO-based device, maintaining 93.4% of the initial efficiency after a 200 h light-soaking at the maximum power point tracking under AM 1.5G irradiation, which is attributed to the robust SnO2/PbS CQD heterojunction under operational conditions. The improved efficiency and operational stability suggest the superiority of the dip-coated SnO2 ETL to its ZnO counterpart, paving a way for the development of high-efficiency and high-stability CQDSCs via WBO-ETL engineering.