Exciton-Mediated Photoconductivity Switching in Organic-Inorganic Hybrid Transistors

Abstract

While organic-inorganic heterogeneous field-effect transistors (FETs) present a compelling platform for optoelectronic devices due to their switchable photoresponse characteristics and multifunctionality, the transient photoconductivity governed by the exciton dynamics in an organic photogating layer remains poorly understood. To address this gap, we integrate two pi-conjugated organic materials, which are poly(3-hexylthiophene) (P3HT) and Phenyl-C61-butyric acid methyl ester (PCBM), with distinct exciton binding characteristics onto inorganic silicon nanowire (Si NW) channels and systematically compare their photoconductive behaviors through both static and time-resolved photoelectrical measurements. Our findings uncover that the weak exciton binding in PCBM renders excitons more susceptible to prolonged optical and electrical stimuli, leading to progressive exciton dissociation and enhanced photogating effects over time in PCBM-Si NW-FETs. In contrast, P3HT, with its relatively stronger exciton binding energy, exhibits a stable and well-defined photoconductivity. Leveraging the predictable, time-independent negative photoconductivity in the P3HT-Si NW-FET, we demonstrate its potential for use as an optically erasable artificial synapse. These findings comprehensively highlight the critical role of dynamic exciton dissociation in an organic photogating layer in reshaping the temporal evolution of photoconductivity in an inorganic transistor framework.