Adjustable Super‐linear Photoresponse via Organic Phototransistors with Graded Active Layer Toward Intelligent Contrast Control

Abstract

AbstractGenerally, photocurrent achieves saturation easily under high light intensity and/or high current density by exciton/carrier quenching; to the best of authors knowledge super‐linear photoresponse has not been observed experimentally in all types of photodetectors before. This study has reported super‐linear photoresponse organic phototransistors (OPTs) based on bulk heterojunction (BHJ) with PM6 as the donor and Y6 as the non‐fullerene acceptor. The super‐linear photoresponse has satisfied that the photocurrent is proportional to the 1.37 power of light intensity (linearity index ∂ = 1.37), in which gain achieves 280% (external quantum efficiency, EQE greater than 1) and detectivity (Dshot*) achieves 1.88 × 1013 Jones at Vg of 5 V. The quick minority carrier release of non‐fullerene acceptor can help reduce the threshold voltage drift and match the transconductance, improving the possibility of obtaining super‐linear response regions. The graded distribution of donor/acceptor is more likely to reduce carrier quenching under high light intensity during the extension of Debye screening layer for effective super‐linear response. By modulating the gate voltage, the linearity index can be adjusted from 0.5 to 2.33, where the super‐linear photoresponse can automatically enlarge the contrast of the image. It has an excellent application prospect in intelligent contrast control in real time image recognition.