| Summary: | Light-modulated lead-free perovskites-based memristors, combining photoresponse and memory, are promising as multifunctional devices. In this work, lead-free double perovskite Cs<sub>2</sub>AgBiBr<sub>6</sub> films with dense surfaces and uniform grains were prepared by the low-temperature sol-gel method on indium tin oxide (ITO) substrates. A memory device based on a lead-free double perovskite Cs<sub>2</sub>AgBiBr<sub>6</sub> film, Pt/Cs<sub>2</sub>AgBiBr<sub>6</sub>/ITO/glass, presents obvious bipolar resistive switching behavior. The <i>R</i><sub>OFF</sub>/<i>R</i><sub>ON</sub> ratio under 445 nm wavelength light illumination is ~100 times greater than that in darkness. A long retention capability (>2400 s) and cycle-to-cycle consistency (>500 times) were observed in this device under light illumination. The resistive switching behavior is primarily attributed to the trap-controlled space-charge-limited current mechanism caused by bromine vacancies in the Cs<sub>2</sub>AgBiBr<sub>6</sub> medium layer. Light modulates resistive states by regulating the condition of photo-generated carriers and changing the Schottky-like barrier of the Pt/Cs<sub>2</sub>AgBiBr<sub>6</sub> interface under bias voltage sweeping.
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