Ligand-Stabilized Reduced-Dimensionality Perovskites

TLDR

Metal halide perovskites have rapidly advanced thin‑film photovoltaic performance, yet their observed instabilities urgently require a solution. The study reports quasi‑2D perovskite films that improve stability while maintaining the high performance of conventional 3D perovskites. DFT reveals that low formation energy, especially under humidity, drives perovskite decomposition, and the authors synthesize quasi‑2D films with tunable dimensionality via stoichiometry, characterized by photophysical studies. DFT shows that phenylethylammonium intercalation adds van der Waals interactions, raising formation energy and improving stability, and the authors achieve the first certified hysteresis‑free planar perovskite solar cell with 15.3 % certified P.

Abstract

Metal halide perovskites have rapidly advanced thin-film photovoltaic performance; as a result, the materials' observed instabilities urgently require a solution. Using density functional theory (DFT), we show that a low energy of formation, exacerbated in the presence of humidity, explains the propensity of perovskites to decompose back into their precursors. We find, also using DFT, that intercalation of phenylethylammonium between perovskite layers introduces quantitatively appreciable van der Waals interactions. These drive an increased formation energy and should therefore improve material stability. Here we report reduced-dimensionality (quasi-2D) perovskite films that exhibit improved stability while retaining the high performance of conventional three-dimensional perovskites. Continuous tuning of the dimensionality, as assessed using photophysical studies, is achieved by the choice of stoichiometry in materials synthesis. We achieve the first certified hysteresis-free solar power conversion in a planar perovskite solar cell, obtaining a 15.3% certified PCE, and observe greatly improved performance longevity.