HPbI₃ as a Bifunctional Additive for Morphology Control and Grain Boundary Passivation toward Efficient Planar...

One of the key aspects contributing to the rapid development of perovskite solar cells is to prepare high-quality perovskite films via morphology control and interface engineering. Here, we demonstrate that the additive HPbI₃ works effectively on both morphology control and grain boundary passivation of CH₃NH₃PbI_{3- x}Cl _x thin films. By inducing HPbI₃ to the crystal transformation process, high-quality perovskite films consisting of micro-sized grains with boundaries passivated by PbI₂ can be readily produced. The perovskite film obtained with HPbI₃ as the additive achieves a much longer carrier lifetime compared to the pristine perovskite film without the additive. Under the optimal HPbI₃ amount (5.0%), the average power conversion efficiency of the planar-heterojunction solar cells is increased by ∼24% to 17.42% from 14.09% for the device without the additive, and the champion efficiency reaches 18.59%. The devices without any encapsulation show impressive shelf stability, retaining more than 85% of the initial efficiency after being stored in ambient environment for over 40 days.