Hybrid Dion–Jacobson 2D Lead Iodide Perovskites

TLDR

Hybrid organic–inorganic perovskites have shown great promise for solar cells, and lower‑dimensional derivatives are emerging with enhanced tunability of physical properties. This study reports the first complete homologous series of Dion–Jacobson 2D lead iodide perovskites. The 2D perovskites follow the formula A'A n‑1Pb nI₃ n+1 (A' = 3‑AMP or 4‑AMP, A = MA), feature uniquely stacked inorganic layers, and DFT analysis indicates that the organic cation indirectly shifts the band gap. The 3AMP series exhibits smaller band gaps than the 4AMP series, and photovoltaic devices using (3AMP)(MA)₃Pb₄I₁₃ achieve a 7.32 % PCE, markedly higher than the 4AMP counterpart.

Abstract

The three-dimensional hybrid organic-inorganic perovskites have shown huge potential for use in solar cells and other optoelectronic devices. Although these materials are under intense investigation, derivative materials with lower dimensionality are emerging, offering higher tunability of physical properties and new capabilities. Here, we present two new series of hybrid two-dimensional (2D) perovskites that adopt the Dion-Jacobson (DJ) structure type, which are the first complete homologous series reported in halide perovskite chemistry. Lead iodide DJ perovskites adopt a general formula A'A n-1Pb nI3 n+1 (A' = 3-(aminomethyl)piperidinium (3AMP) or 4-(aminomethyl)piperidinium (4AMP), A = methylammonium (MA)). These materials have layered structures where the stacking of inorganic layers is unique as they lay exactly on top of another. With a slightly different position of the functional group in the templating cation 3AMP and 4AMP, the as-formed DJ perovskites show different optical properties, with the 3AMP series having smaller band gaps than the 4AMP series. Analysis on the crystal structures and density functional theory (DFT) calculations suggest that the origin of the systematic band gap shift is the strong but indirect influence of the organic cation on the inorganic framework. Fabrication of photovoltaic devices utilizing these materials as light absorbers reveals that (3AMP)(MA)3Pb4I13 has the best power conversion efficiency (PCE) of 7.32%, which is much higher than that of the corresponding (4AMP)(MA)3Pb4I13.