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 films with a root-mean-square roughness of 3.3 μm (>8 μm for conventional E-spray). The resulting x-ray detector exhibited a high sensitivity of 2401 μC Gy⁻¹ cm⁻² and a low detection limit of 5.68 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.