Organic phototransistors (OPTs) are appealing devices for the fabrication of low-cost, tuneable, and highly sensitive light detectors. This study investigates the potential of single-component OPTs based on the non-fullerene acceptor Y6 to detect near-infrared (NIR) light. Y6 films are deposited via blade coating and subjected to thermal annealing between 200°C and 250°C.
Morphological and structural characterization reveals a transition from amorphous to a polycrystalline phase above 200°C. Electrical measurements demonstrate enhanced electron mobility and reduced hysteresis in annealed devices. Under 840 nm illumination, amorphous films exhibit photoconductive behavior, while polycrystalline films show photogating/photogain effects, resulting in significantly higher photoresponsivity and faster transient response times.
The highest photoresponsivity achieved is 127 A·W−1 and a shot-noise-limited specific detectivity of 6·1012 Jones (6·1010 Jones under full noise analysis) are achieved in polycrystalline devices under low NIR light intensity (0.32 µW·cm−2) at VDS = VGS = 10 V, associated with enhanced charge carrier mobility rather than enhanced free charge generation.
The devices also exhibit high cycling stability under continuous measurements and long-term shelf-stability when encapsulated. These findings establish thermally annealed Y6 films as a viable single-component material for efficient NIR photodetection.
The research, titled "Crystallinity Effects on Near-Infrared Photoresponse in Y6-Based Organic Phototransistors", has been published in the journal Small and involves Lluís Casabona-Cendra, Carme Martínez-Domingo, Vick Y. Qiu, Xiaocen Dong, Dean Kos, Sergi Riera-Galindo, Mariano Campoy-Quiles, Ji-Seon Kim, and Marta Mas-Torrent, members of the M4ELC Sustainable Electronics group at ICMAB.
