An A2B2O7‐Type High‐Entropy Oxide for Efficient Photoelectrochemical Photodetector with Excellent Long‐Term Stability

Abstract Optoelectronics with excellent long‐term stability is meaningful for practical applications. Herein, for the first time, an A 2 B 2 O 7 type high‐entropy oxide of (La 0.2 Ce 0.2 Nd 0.2 Gd 0.2 Bi 0.2 ) 2 Ti 2 O 7 (ATO) is synthesized and applied for photoelectrochemical photodetection. The lattice distortion, highly dispersed metal composition, and exposed active sites of ATO are beneficial for the fast separation and transmission of photogenerated electron/hole pairs, endowing ATO‐based devices with good photodetection performance. Both the density functional theory calculations and the nondegenerate transient absorption spectroscopy demonstrate the good optoelectronic properties of ATO. The systematic experimental studies reveal the tunable photodetection capability of ATO‐based photodetector (PD) in the visible region. A photocurrent of 772.00 nA cm −2 and a responsivity of 4.02 µA W −1 can be achieved as the PD in 1.0 m KOH with the bias potential of 0.6 V. Importantly, the robust and reproducible ON/OFF signals of the PD can be verified and there is only ≈5.00% attenuation in photocurrent even after 6 months, revealing the great potential of high‐ entropy oxides for practical applications.