Enhanced charge collection with passivation of the tin oxide layer in planar perovskite solar cells

Abstract

Tin oxide is an excellent candidate to replace mesoporous TiO₂ electron transport layers (ETLs) in perovskite solar cells. Here, we introduced a SnO₂ layer by a low-temperature solution process, and investigated its morphology, opto-physical and electrical properties affecting the device performance. We reveal that low-temperature processed SnO₂ is self-passivating in nature, which leads to a high efficiency. To further enhance the blocking effect, we combined a compact TiO₂ underlayer with the SnO₂ contact layer, and found that the bi-layered ETL is superior compared to single layers. The best device shows photovoltaic values in a planar structure with a short-circuit current density (J_sc) of 22.58 mA cm⁻², an open-circuit voltage (V_oc) of 1.13 V, a fill factor (FF) of 0.78, and a power conversion efficiency (PCE) of 19.80% under 1 sunlight illumination.