Long Carrier Diffusion Length and Efficient Charge Transport in Thick Quasi-Two-Dimensional Perovskite Solar Cells Enabled by Modulating Crystal Orientation and Phase Distribution
Lvpeng Yang, Jishan Shi, Youzhi Wu, Xin Jin, Tong Bie, Chunlong Hu, Wenxi Liang, Yerun Gao, Meichen Xu, Ming Shao
Abstract
The applications of quasi-two-dimensional (quasi-2D) perovskite solar cells (PSCs) are limited by their insufficient charge transport, and the underlying charge transport mechanism is not clear yet. Herein, we report a simple strategy for achieving efficient charge transport in the quasi-2D perovskite FPEA2MAn–1PbnI3n+1 (⟨n⟩ = 4) by combining the crystal orientation control via the hot-casting method and the regulation of phase composition and distribution using methylammonium chloride (MACl) additives. The steady and transient optical spectra reveal that the synergistic effect of hot-casting processing and MACl additive leads to the formation of 3D-like phases, acting as highly conductive pathways to boost charge collection and transport in quasi-2D perovskite films. These specific phase heterogeneities result in an extraordinary long carrier diffusion length of 1.2 μm. The resultant quasi-2D PSCs show a high power conversion efficiency of 17.5%. Notably, this remarkable efficiency is achieved for a relatively thick film (∼623 nm), which is much thicker than most reported efficient quasi-2D PSCs (200–500 nm). Moreover, our PSCs have demonstrated excellent environmental stability and thermal stability. Our results highlight that controlling the crystal orientation and multiphase distribution of quasi-2D perovskites is very promising to push the efficiency of quasi-2D PSCs approaching their three-dimensional (3D) counterparts.