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

In this paper, three kinds of SnO 2 precursors were comparatively investigated for low temperature solution-processed SnO 2 films as electron transport layers (ETL) of CsPbBr 3 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 SnO 2 . All-inorganic hole-transport-layer-free planar CsPbBr 3 PSCs with an architecture of FTO/SnO 2 /CsPbBr 3 /carbon were fabricated. The best-performing device with SnO 2 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 7.36 mA cm − 2 , an open-circuit voltage of 1.29 V, 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 TiO 2 -ETL so far. Moreover, the CsPbBr 3 devices without encapsulation exhibited good stability after being stored under ambient conditions with a relative humidity of ∼ 4 0 % at room temperature over 1000 h and 60 ∘ C for 720 h, respectively. The results promise the commercial potential of CsPbBr 3 PSCs using reflux condensation low-temperature solution-processed SnO 2 as ETLs for flexible polymer photovoltaic applications.