Solution-processed Cu-doped SnO2 as an effective electron transporting layer for High-Performance planar perovskite solar cells

Abstract

A high-quality electron transport layer (ETL) is indispensable for effective and stable planar perovskite solar cells (PSCs). Tin oxide (SnO2) is considered the most promising alternative to TiO2 as ETL due to its excellent optical and electrical properties. However, some of improvements need to be carried out for intrinsic SnO2, such as conductivity, energy loss, and lattice mismatch in the SnO2/perovskite interface. Herein, the Cu-doped SnO2 (Cu: SnO2) as ETL has been made through mixing the copper salt precursor solution with SnO2 colloidal solution in room-temperature solution-processed. The Cu incorporated into SnO2 increases the conductivity of ETL and uplifts the conduction band to obtain a more suitable band alignment in SnO2/perovskite interface for relieving the energy barrier in the charge transporting. Moreover, it further improves the quality of perovskite films with the enhanced crystallinity, enlarged grain size, which have an impact on light absorption and reduction of defect states for the perovskite layer. The power conversion efficiency (PCE) of the prepared planar PSCs with Cu:SnO2 ETL exceeds 21%, compared with the SnO2-based PSCs (19.63%), and the long-term stability was improved.