High Performance Flexible Organic Phototransistors with Ultrashort Channel Length

Organic phototransistors with high responsivity and sensitivity to light irradiance have great potential applications in environmental monitoring, space exploration, security, image sensors and healthcare systems. In this manuscript, a novel polymer bulk heterojunction field effect phototransistor with ultrashort channel length (tens of nanometers) and ultrahigh sensitivity to visible light was proposed. Due to the nanoscale channel and bulk heterojunction structure, a high-performance phototransistor with high responsivity of 750 A/W, photosensitivity of 1.0 × 106, and detectivity as high as 4.54 × 1015 Jones was demonstrated under 720 nm light illumination with 0.1 mW/cm2 intensity, which was even better that those lateral organic phototransistors. Moreover, organic phototransistors with ultrashort channel length were investigated for the first time on a flexible substrate, which exhibited outstanding mechanical flexibility due to their unique designs. Further investigation of the correlation between the morphology of bulk heterojunction blends and the device photoresponse performance indicated that the photoelectric properties of the devices could be effectively enhanced by controlling the morphology of semiconducting layers. More importantly, this work provided first clear experimental evidence that the surface area of semiconducting crystals would significantly impact dissociation of photoinduced excitons and transfer and recombination of photogenerated carriers, which is crucial for photoelectric performance of phototransistors. This work provided critical guidelines for the development of high performance flexible organic phototransistors, which opened up the doors of opportunity for organic phototransistors applications in a wide range of organic electronics.