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) ₂ Pb ₃ I ₆ , 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.