Dependence of Precursors on Solution-Processed SnO2 as Electron Transport Layers for CsPbBr3 Perovskite Solar Cells

In this paper, three kinds of SnO2 precursors were comparatively investigated for low temperature solution-processed SnO2 films as electron transport layers (ETL) of CsPbBr3 perovskite solar cells (PSCs). It was found that the precursor state and solvent type played an important role on the crystallinity and film-forming performance of SnO2. All-inorganic hole-transport-layerfree planar CsPbBr3 PSCs with an architecture of FTO/SnO2/CsPbBr3/carbon were fabricated. The best-performing device with SnO2 as ETL by reflux condensation sol spin- coating technique delivered a champion power conversion efficiency (PCE) as high as 6.27%, with a short-circuit current density of 7.36mAcm-2, an open-circuit voltage of 1.29V, and a fill factor of 65.9%. It was comparable to the highest PCE record 6.7% of the device with the same structure based on TiO2-ETL so far. Moreover, the CsPbBr3 devices without encapsulation exhibited good stability after being stored under ambient conditions with a relative humidity of similar to 40% at room temperature over 1000 h and 60.C for 720 h, respectively. The results promise the commercial potential of CsPbBr3 PSCs using reflux condensation low-temperature solution-processed SnO2 as ETLs for flexible polymer photovoltaic applications.