Highly electroluminescent and stable inorganic CsPbI2Br perovskite solar cell enabled by balanced charge transfer

Compared to the hybrid perovskite, inorganic perovskite has potential to improve the thermal stability, but the photoelectric performance is limited by the film defect and unbalanced charge transfer. In this work, we pre-treat SnO2 layer with fullerene-ethylenediamine derivatives (C60-EDA and C70-EDA) and post-treat the CsPbI2Br perovskite film using 5-aminovaleric acid hydrobromide (5-AVABr), leading to the high photovoltaic/electroluminescent (PV/EL) performance. Due to the improved film-forming property, SnO2:C60-EDA and SnO2:C70-EDA induced large-grain CsPbI2Br film with low defect density and superior interface connectivity. The combined pre-post treatments balance the charge transfer at N-I-P interface for injection and extraction, respectively, leading to the efficient inorganic perovskite bifunction device (PBD). The target CsPbI2Br device achieved a PV efficiency of 16.58% (stabilized to 16.30%) with a Voc of 1.32 ± 0.06 V in the PV mode and the EL external quantum efficiency (EQEEL) of 6.2% in the EL mode, much higher than the control device (PV efficiency of 12.06% and EQEEL of 1.0%). Thus, we demonstrated the reciprocity relation between PV and EL modes that a great solar cell needs to be a great LED. Besides, the performance can still maintain 93% and 80% of its initial values when stored in dry air atmosphere for 65 days and heated at 85 °C for 12 days, respectively. The stable PBD has potential to utilize the solar energy more efficiently for smart power supply in the electronics.