Trap Induced Negative Response in Cs ₂ AgBiBr ₆ Photodetectors for In‐Memory Sensing and Computing

Abstract In‐memory sensing and computing always used optoelectronic memristors for storage and calculation. Double photoelectric states are needed in integration in optoelectronic memristors. In this work, all‐inorganic lead‐free double perovskite Cs ₂ AgBiBr ₆ (CABB) has been used as a photon absorber. To obtain double photoelectric states for possible application, surface traps in CAAB film provide the possibility. Simultaneous emergence of diverse state with both positive photoconductivity (PPC) and negative photoconductivity (NPC) effects satisfies the artificial‐intelligent sensor demands, which integrate memory and computation in single device, presenting extraordinary modern computing potential. Under 400 nm illumination, CABB film sensor presents PPC‐effects, where photocurrent enlarges as light intensity increases, which PPC responsivity is 0.85 A W ⁻¹ . However, under 520 nm illumination, it presents NPC‐effects, where photocurrent decreases as light intensity increases, which NPC responsivity is 0.24 A W ⁻¹ . As experimental characterization and numerical simulation shows, NPC is originated from space‐charges accumulation in trap‐states at the interface of CABB and ITO. Traps attract holes and impede electron transfer, reducing carrier concentration and carrier mobility, then enhancing NPC performance. Double effects provide possibility in optoelectronic memristor, where a process of image encryption and operator mapping for calculation are shown in this work, possessing remarkable prospects and providing opportunities for photonic‐chips development.