Synchronous dimension-crystallization engineering enables highly efficient 2D/3D tin perovskite solar cells

Abstract

Tin perovskite films with two-dimensional/three-dimensional (2D/3D) heterostructures show promise for high performance lead-free perovskite solar cells (PSCs); however, they face challenges due to the undesirable carrier transport caused by intrinsic multi-quantum wells, and susceptible crystallization kinetics caused by the introduction of organic spacer cations. We herein propose and validate a strategy that could simultaneously address these challenges based on synchronous dimension-crystallization engineering in 2D/3D tin perovskite films. Different from the conventional dimension engineering that relies on precise n-phase control, the employed 4-guanidinium benzoate hydrochloride (GBAC) in the present work has an unforeseen desorption effect between phenylethylamine (PEA) and the perovskite, which leads to a direct transition from the 2D to the 3D phase. It is also found that introducing GBAC results in the formation of elongated organic–inorganic hybrid chains, which improves the crystallization process of the films by accelerating both nucleation and growth rates. By virtue of these merits, the resulting tin PSCs achieve a champion power conversion efficiency of 15.02%, together with exceptional long-term stability with 87% remaining after 4000 h and 80% after 400 h under working at the maximum power point.