Diffusion interface layer controlling the acceptor phase of bilayer near-infrared polymer phototransistors with ultrahigh photosensitivity

The narrow bandgap of near-infrared polymers is a hindrance to their performance improvement. Here, authors present a diffusion interface layer between the channel layer and bulk heterojunction layer of a phototransistor, using solvent vapor annealing as a way of overcoming this barrier. The narrow bandgap of near-infrared (NIR) polymers is a major barrier to improving the performance of NIR phototransistors. The existing technique for overcoming this barrier is to construct a bilayer device (channel layer/bulk heterojunction (BHJ) layer). However, acceptor phases of the BHJ dissolve into the channel layer and are randomly distributed by the spin-coating method, resulting in turn-on voltages (V-o) and off-state dark currents remaining at a high level. In this work, a diffusion interface layer is formed between the channel layer and BHJ layer after treating the film transfer method (FTM)-based NIR phototransistors with solvent vapor annealing (SVA). The newly formed diffusion interface layer makes it possible to control the acceptor phase distribution. The performance of the FTM-based device improves after SVA. V-o decreases from 26 V to zero, and the dark currents decrease by one order of magnitude. The photosensitivity (I-ph/I-dark) increases from 22 to 1.7 x 10(7).

Automated summary

The authors propose a method to overcome the narrow bandgap of near-infrared polymers by using solvent vapor annealing. They form a diffusion interface layer between the channel layer and bulk heterojunction layer, which leads to an improvement in device performance.