Efficient all-inorganic CsPbIBr2 perovskite solar cells with an open voltage over 1.33 V by dual-additive strategy

The internal non-radiative recombination and high trap-state density (Ntrap) in perovskite layer have severely limited the progress of low-temperature processed CsPbIBr2 perovskite solar cells (PSCs). In this work, cesium acetate (CsAc) and hydrogen lead triiodide (HPbI3) dual-additives are employed to tune the properties of CsPbIBr2 film prepared by low-temperature process. The CsAc material is used to modify CsPbIBr2 surface and optimize the CsPbIBr2/carbon electrode interface, while HPbI3 additive is employed to dope perovskite layer. The dual-additive strategy is used to optimize the microstructure and regulate the optoelectrical characteristics of carbon-based CsPbIBr2 PSCs. It is found that CsAc can passivate the vacancy defect of Br−, reduce the energy loss (Eloss) and enhance the open-circuit voltage (Voc) of PSCs. The HPbI3 additive works to optimize the crystallization process, resulting in the high-quality CsPbIBr2 films with better crystallinity and morphology. The modified films by CsAc and HPbI3 dual-additive demonstrate smaller band gap, better light absorption, reduced trap-state density (Ntrap) and suppressed carrier recombination. The optimized carbon-based PSCs modified by the dual-additive achieve a champion power conversion efficiency of 9.18% with a Voc of 1.334 V, more matched energy-level, reduced Eloss and promoted charge transfer. Moreover, the modified PSCs without encapsulation show improved long-term humid stability. Our work provides a facilitated method to prepare an efficient and stable CsPbIBr2 PSCs by low-temperature process.