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

Tao Han,Xiaoyi Huang,Chunzhi Jiang,Shufang Ding,Xiaofeng Zhang,Zewen Zhou,Xuehua Hou,Ning Shen,Linlin Liu,Zejiang Wang

doi:10.1038/s41467-022-28922-4

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 (Vo) 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. Vo decreases from 26 V to zero, and the dark currents decrease by one order of magnitude. The photosensitivity (Iph/Idark) increases from 22 to 1.7 × 107.

Highlights

The narrow bandgap of near-infrared (NIR) polymers is a major barrier to improving the performance of NIR phototransistors
The structure of the device consists of Si/SiO2/PDPP3T/Au/ PDPP3T:PC61BM (Fig. 1a), among which the film transfer method (FTM)-based poly(diketopyrrolopyrrole-terthiophene) (PDPP3T) and PDPP 3T:PC61BM layers were treated with solvent vapor annealing (SVA)
A diffusion interface layer, instead of a mutual dissolution interface layer, was formed between the channel transport layer and bulk heterojunction layer to prevent the random distribution of acceptor phases

Summary

Introduction

The narrow bandgap of near-infrared (NIR) polymers is a major barrier to improving the performance of NIR phototransistors. Acceptor phases of the BHJ dissolve into the channel layer and are randomly distributed by the spincoating method, resulting in turn-on voltages (Vo) and off-state dark currents remaining at a high level. 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 NIR polymer materials used in phototransistors have a narrow bandgap, which always leads to a high exciton binding energy and the difficult dissociation of photogenerated excitons[7]. A high concentration of acceptor phases in traditional single-layer bulk heterojunction (BHJ) photodetectors is needed, which can lead to electron/hole recombination[9]

Methods

Results

Conclusion