Low-Temperature Perovskite Crystallization Suppresses Interfacial Thermal Stress for Robust and High-Resolution Flat-Panel X-Ray Imaging.

Abstract

Interfacial thermal stress is a common issue limiting the performance of perovskite optoelectronics, particularly x-ray detectors. This challenge originates from thermomechanical incompatibility: conventional high-temperature perovskite crystallization induces severe interfacial thermal stress upon cooling, triggering film delamination and cracking. Herein, through solvent engineering and intermediate design, we demonstrate, for the first time, the low-temperature formation of perovskite thick films, mitigating this issue at its origin. This is achieved by a new perovskite ink formulation containing highly volatile 2-methoxyethanol (2-ME) and monodentate coordinating 1-cyclohexyl-2-pyrrolidone (CHP). This combination yields a new intermediate, (CHP)₂Pb₃I₆, that largely decouples nucleation from growth and lowers the crystallization temperature from 135 to 75°C. This reduction, along with an improved wettability, decreases the interfacial thermal stress by ∼75% and doubles the interfacial adhesion strength. Consequently, robust integration of perovskite thick films with an indium-gallium-zinc-oxide (IGZO) thin-film transistor (TFT) backplane is achieved. The resulting flat-panel imager delivers a spatial resolution of 4.73 lp mm^-1 (0.59 lp pix^-1) when the modulation transfer function (MTF) reaches 0.2, outperforming commercial amorphous selenium (α-Se) and previous perovskite-based imagers. This work elucidates intermediate-regulated crystallization thermodynamics and opens avenue for integrating monolithic perovskite optoelectronics onto temperature‑sensitive substrates.