Flexible, Low-Voltage, and n-Type Infrared Organic Phototransistors with Enhanced Photosensitivity via Interface Trapping Effect

Flexible and low-voltage near-infrared organic phototransistors (NIR OPTs) were prepared with a low-band gap donor–acceptor conjugated polymer as the semiconductor layer and n-octadecyl phosphonic acid modified anodic alumina (AlOx/ODPA) as the insulating layer. The phototransistors exhibit the typical n-type transistor characteristics at a voltage below 5 V. The photosensitivity of phototransistors can be enhanced by regulating the packing densities of the ODPA self-assembled monolayers and forming different trap states. The enhanced OPTs exhibit good photosensitivity to 808–980 nm NIR with the photocurrent/dark current ratio and photoresponsivity as high as 5 × 103 and 20 mA W–1, respectively, benefiting from the charge-trapping effect at the AlOx/ODPA interface. The OPTs also present a fast optical switching speed of 20/30 ms and an excellent mechanical flexibility. The outstanding performance of the NIR OPTs indicates that the development of wearable electronics is, indeed, possible.