Strain‐Stabilized CsPbI3 Perovskite via Organopolysilazane for Efficient Solar Cells with Efficiency over 19%

Abstract Principally, all‐inorganic perovskite crystals, such as CsPbI 3 , possess higher thermal stability than their organic–inorganic hybrid counterparts, like CH 3 NH 3 PbI 3 , due to the type of chemical bond variants. However, considering a retained strain in these stiff films, it is a challenge to stabilize CsPbI 3 within the photoactive phase for photovoltaic application under ambient conditions. This article reports organopolysilazane (OPSZ) as a strain compensation layer that regulates the tense strain during the annealing process, a very attractive feature for all‐inorganic perovskite solar cells with a CsPbI 3 active layer. When depositing OPSZ onto the surface of CsPbI 3 film for thin‐film solar cell devices with FTO/c‐TiO 2 /CsPbI 3 /spiro‐OMeTAD/Au architecture, an efficiency of 19.12% is achieved under standard illumination test conditions. This strain compensation layer offers a viable pathway to develop efficient and stable solar cells with inorganic perovskite crystalline thin films for scale‐up and practical applications.