High-member low-dimensional Sn-based perovskite solar cells

Sn-based perovskites are promising thin-film photovoltaic materials for their ideal bandgap and the eco-friendliness of Sn, but the performance of Sn-based perovskite solar cells is hindered by the short carrier diffusion length and large defect density in nominally-synthesized Sn-based perovskite films. Herein we demonstrate that a long carrier diffusion length is achievable in quasi-2D Sn-based perovskite films consisting of high-member low-dimensional Ruddlesden—Popper (RP) phases with a preferred crystal orientation distribution. The key to the film synthesis is the use of a molecular additive formed by phenylethy-lammonium cations and optimally mixed halide—pseudohalide anions, which favorably tailors the quasi-2D Sn-based perovskite crystallization kinetics. The high-member RP film structure effectively enhances device short-circuit current density, giving rise to an increased power conversion efficiency (PCE) of 14.6%. The resulting device demonstrates a near-unity shelf stability upon 1,000 h in nitrogen. A high reproductivity is also achieved with a count of 50 devices showing PCEs within a narrow range from minimum 13.0% to maximum 14.6%.