Simultaneous Photomultiplication Improvement and Response Acceleration for High-Performance Lateral Polymer Photodetectors Based on Bulk Heterojunction
Meihua Shou, Qinglei Zhang, Shicheng Xiong, Tao Han, Jiadong Zhou, Nan Zheng, Zengqi Xie, Linlin Liu
Abstract
In organic photodetectors, photomultiplication is mainly originated from interfacial and/or bulk charge traps, which induces slow response due to the slow release of trapped charges and strongly limits the optimization of the overall performance. This study has exhibited a remarkable case that the gain (>1) and response speed of the lateral photodetectors are promoted simultaneously and effectively by increasing the trap ratio. For lateral photodetectors with silver nanoparticles and PDPPBTT:PC61BM bulk heterojunction, the gain increases from 12.7 to 19.8 and the fall time decreases from 313.4 to 172.9 ms as the PC61BM ratio increases from 5:1 to 1:1. The lateral photodetector structure with a long electrode distance has been testified to play the key role for simultaneous promotion compared with vertical photodiodes, allowing the charges to trap well in the PC61BM-rich phase at a high PC61BM ratio and accumulation of multiple built-in electric fields. The long channel distance and silver nanoparticles also effectively restrain the increment of dark current with PC61BM loading, resulting in a high detectivity of 1.7 × 1012 Jones under 0.031 mW cm–2 @ 820 nm. It is of great theoretical and practical value for the high-performance photodetectors with simultaneous high photomultiplication and quick response.