Diffusion interface layer controlling the acceptor phase of bilayer near-infrared polymer phototransistors with ultrahigh photosensitivity
Tao Han, Zejiang Wang, Ning Shen, Zewen Zhou, Xuehua Hou, Shufang Ding, Chunzhi Jiang, Xiaoyi Huang, Xiaofeng Zhang, Linlin Liu
Abstract
Abstract 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 × 10 7 .