Photomultiplication Behavior of Chlorophyll-Based Photodetector under Biased Voltage
Yuting Sun, Jian Jiang, Tian‐Fu Xiang, Aijun Li, Ziyan Liu, Yuanlin Li, Shin‐ichi Sasaki, Hitoshi Tamiaki, Xiaofeng Wang
Abstract
In this study, we fabricated a photodetector (PD) with two types of chlorophyll derivatives, namely, zinc methyl 3-devinyl-3-hydroxymethyl-pyropheophorbide-a (ZnChl) and methyl 13 1 -deoxo-13 1 -dicyanomethylene-pyropheophorbide-a (H 2 Chl′), via a two-step drop-coating process. In the absorption range of ZnChl/H 2 Chl′ films, the maximum external quantum efficiency of ZnChl/H 2 Chl′-based devices reached 1363% at −8 V and 1345% at 2.5 V, exhibiting the photomultiplication (PM) phenomenon. The PM phenomenon of ZnChl/H 2 Chl′-based devices is attributed to hole tunneling injection from the external circuit assisted by electron accumulation in the ZnChl and H 2 Chl′ under light illumination. Through the investigation of the responsivity ( R ) of ZnChl/H 2 Chl′-based devices, it has been found that achieving a high R is easier under forward bias compared with reverse bias (7706 mA/W at −8 V and 7629 mA/W at 2.5 V). The organic PDs based on ZnChl/H 2 Chl′ exhibit PM behavior, offering a promising approach to improve the device’s responsivity.