Bilayer chlorophyll-based bio-photodetector based on Z-type charge transfer process

Abstract

We have successfully prepared a bio-photodetector based on chlorophyll derivatives as all photosensitive materials. Zinc methyl 3-devinyl-3-hydroxymethyl-pyropheophorbide-a (Chl-A) and methyl 13¹-deoxo-13¹-dicyanomethylene-pyropheophorbide-a (Chl-D) were used as electron acceptor and donor, respectively, where the two formed a heterojunction. Although the energy alignment of the photoactive layers of the device studied here is different from that of traditional photodetectors, the device can work well in a self-driven mode. The device has an optimized configuration, i.e., indium tin oxide (ITO)/ZnO/Chl-A/Chl-D/MoO₃/Ag, and exhibited excellent performance at self-biasing. When ZnO was applied as the electron transport layer in the ITO/ZnO/Chl-A/Chl-D/MoO₃/Ag bio-photodetector device, the dark current density reduced significantly. Besides, the responsivity of the device reached 92.66 mA W⁻¹, which is an increase by ~34 times compared to the ITO/Chl-A/Chl-D/MoO₃/Ag device, and the specific detectivity reached 2.48 × 10¹¹ Jones.