Omnidirectional diffusion of organic amine salts assisted by ordered arrays in porous lead iodide for two-step deposited large-area perovskite solar cells

Abstract

The perovskite film prepared by traditional two-step sequential deposition possesses numerous defects and excess lead iodide (PbI₂), which is mainly due to the formation of a dense PbI₂ layer and the incomplete solid–liquid reaction. It has been shown that the presence of the PbI₂ species has some positive effects on the power conversion efficiency (PCE), but the random distribution of excess PbI₂ can be detrimental to the device stability. Herein, we demonstrate the feasibility of fabricating a porous PbI₂ layer with ordered array structure by integrating a succinamide (SA) additive with a nanoimprinting technology, which can confine the organic amine salts in PbI₂ arrays to facilitate the omnidirectional diffusion and realize sufficient conversion to perovskites. Consequently, an unencapsulated device (active area of 0.04 cm²) is obtained with 23.56% efficiency and excellent long-term humidity stability (∼90% efficiency retention after 1800 h) in ambient air (relative humidity of 50 ± 5%). Moreover, the fabricated perovskite solar cell (1.01 cm²) and module (14.63 cm²) achieve impressive efficiencies of 21.57% and 16.42%, respectively. This work paves the way for the expansion of the two-step sequential deposition method from the laboratory to the large-scale fabrication of high-performance perovskite photovoltaic devices.