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

Principally, all-inorganic perovskite crystals, such as CsPbI3, possess higher thermal stability than their organic-inorganic hybrid counterparts, like CH3NH3PbI3, due to the type of chemical bond variants. However, considering a retained strain in these stiff films, it is a challenge to stabilize CsPbI3 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 CsPbI3 active layer. When depositing OPSZ onto the surface of CsPbI3 film for thin-film solar cell devices with FTO/c-TiO2/CsPbI3/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.