Controllable Photoluminescence Modulation of 2D Hybrid Perovskite Single-Phase Derivatives via Inorganic Skeleton Thickness Regulation

The modulation of photoluminescence (PL) properties has great application prospects in the optical and photoelectric fields. Two-dimensional hybrid perovskites exhibit exceptional structural tunability and superior optoelectronic properties, making them promising for advanced photoluminescent applications. However, synthesizing pure multilayer single crystals remains challenging, hindering precise PL modulation. Herein, a series of two-dimensional hybrid perovskite single crystals (i-BA)₂MA_n–1Pb_nBr_3n+1 (where i-BA = isobutylammonium, MA = methylammonium, and n = 1–4 expressed as n1–n4) with varying inorganic framework thicknesses were synthesized. Interestingly, a red shift of PL in these homologues was observed with the change in color from white (n = 1) to green (n = 4); the emission wavelengths were tuned from 430 to 528 nm. Notably, the PL quantum yields increased as the inorganic layer thickness increased from n = 2 to n = 4. Furthermore, we developed green light-emitting devices and polydimethylsiloxane (PDMS)-based flexible luminescent patterns through employing the pure n4 phase. These findings highlight the pivotal role of structural tuning in modulating PL and demonstrate the potential of these single-phase derivatives for advancing solid-state lighting applications.