Coffee-Ring-Suppressed Electrospray of Thick Cs2TeI6 Film for high-sensitivity direct X-ray Detector

Metal halide Perovskites have recently emerged as promising candidates for direct-conversion X-ray detectors due to their high X-ray attenuation coefficient and favorable transport behavior. However, the fabrication of thick (>10 μm), large-area perovskite films with spatial uniformity remains a critical challenge, primarily limited by the coffee-ring induced defects. Here, we developed a modified electrospray (E-spray) method for coffee-ring-suppressed thick Cs2TeI6 films, incorporating two key innovations: (1) a mesoporous Al2O3 modification layer was used to slow down the solute transportation inside the spray droplets, and (2) trimethylbenzene additive was used to establish a counter-directed Marangoni flow inside the droplet. The modified E-spray process yielded 15 μm-thick Cs2TeI6 film with root-mean-square roughness of 3.3 μm （>8 μm for conventional E-spray）. The resulting X-ray detector exhibited a high sensitivity of 2020μC Gy-1 cm-2 and a low detection limit of 6.81 nGys-1. Our work demonstrates a generalizable E-spray strategy for thickness-scalable perovskite films, addressing the critical trade-off between thickness and uniformity. The achieved detector performance suggests potential for low-dose medical imaging applications.