Interlayer Exciton Polarons in Mesoscopic V 2 O 5 for Broadband Optoelectronic Synapses

Abstract Persistent photoconductivity and optoelectronic synaptic behavior are demonstrated in solution‐processed mesoscopic α‐phase vanadium pentoxide (V 2 O 5 ) thin films. First‐principles simulations coupled with the two‐site Holstein polaron hopping model show that vacancies at the terminal oxygen position lead to long recombination times because photoexcited electrons and holes reside on different layers separated by the van der Waals gap, forming a weakly coupled interlayer exciton polaron. Mid‐gap polaronic states also significantly broaden the photoresponse of the films to span across visible and infrared wavelengths. By controlling the amplitude/intensity, duration, and/or number of optical pulses, tunable optoelectronic memory functions, such as short‐term and long‐term plasticity, are experimentally established in V 2 O 5 ‐based optoelectronic synapses. Device fabrication was extended to mechanically flexible ultrathin glass substrates. Flexible optoelectronic synapses maintained high performance after 150 bending cycles.