SnO₂-rGO nanocomposite as an efficient electron transport layer for stable perovskite solar cells on AZO substrate

Electron transport layer (ETL) plays an important role in realizing efficient and stable perovskite solar cells (PSCs). There are continuous efforts in developing new types of low cost ETLs with improved conductivity and compatibility with perovskite and the conducting electrode. Here, in order to obtain high efficient and stable PSCs on ZnO:Al (AZO) substrate, reduced graphene oxide (rGO) is incorporated into SnO₂ nanoparticles to form composite ETL. For planar PSC on AZO substrates, SnO₂-rGO with a low incorporation ratio of 3 wt% rGO significantly enhances the device short circuit current density (J _sc) and the fill factor when compared to the device with pristine SnO₂ ETL, leading to an overall power conversion efficiency of 16.8% with negligible hysteresis. The effectiveness of the excited charge transfer process of SnO₂-rGO ETL is revealed by time-resolved photoluminescence decay, and by electrochemical impedance spectrum measurements. Furthermore, the solar cell stability is also enhanced due to the incorporation of rGO in the ETL. This work provides a low cost and effective ETL modification strategy for achieving high performance planar PSCs.