Abstract
With growing interest in organic phototransistors, as not only sensors but also neuromorphic computing elements, the vast majority of research investigates structures comprising Ohmic source/drain contacts. Here, it is shown how source-gated transistors (SGTs), in which a source contact barrier dominates electrical characteristics, can be implemented as phototransistors. Organic photo-SGTs (OPSGTs) based on vacuum-processed small-molecule dinaphtho[2,3-b:2′,3′-f]thieno[3,2-]thiophene (DNTT) demonstrate low saturation voltage, exceptional tolerance to channel length variation, and photo-to-dark current ratio (PDCR) peaks over 106 for 819 µW broad spectrum incident light power. At zero gate-source voltage, the PDCR reaches 104, showing promise for simple sensor circuit implementation in medical and wellbeing applications.