Lattice-Gradient Perovskite KTaO 3 Films for Ultra-Stable and Low-Dose X-Ray Detector.

Conventional indirect X-ray detectors employ scintillating phosphors to convert X-ray photons into photodiode-detectable visible photons, leading to low conversion efficiencies, low spatial resolutions, and optical crosstalk. Consequently, X-ray detectors that directly convert photons into electric signals have long been desired for high-performance medical imaging and industrial inspection. Although emerging hybrid inorganic-organic halide perovskites, such as MAPbI 3 and MAPbBr 3 , exhibit high sensitivity, they have salient drawbacks including structural instability, ion motion, and the use of toxic Pb. Here we report an ultrastable, low-dose X-ray detector comprising KTaO 3 perovskite films epitaxially grown on a Nb-doped strontium titanate substrate using a low-cost solution method. The detector exhibits a stable photocurrent under high-dose-irradiation, high-temperature (200°C), and aqueous conditions. Moreover, the prototype KTaO 3 -film-based detector exhibits a 150-fold higher sensitivity (3150 μC Gy air -1 cm -2 ) and 150-fold lower detection limit (<40 nGy air s -1 ) than those of commercial amorphous α-Se-based direct detectors. Systematic investigations revealed that the high stability of the detector originates from the strong covalent bonds within the KTaO 3 film, whereas the low detection limit is due to a lattice-gradient-driven built-in electric field, yielding an extremely low dark current. This study unveils a new path toward the fabrication of green, stable, and low-dose X-ray detectors using oxide perovskite films, which have significant application potential in medical imaging and security operations. This article is protected by copyright. All rights reserved.