Effects of Asymmetric Source-Drain Electrodes and Their Modifications on the Operation of Organic Phototransistors

Asymmetric source and drain (S-D) electrodes and their interfacial modifications have significant effects on the charge injection and transport in organic field-effect transistors, however their effects on the operation and performance of organic phototransistors (OPTs) are unknown. Herein, OPTs with symmetric (Ag-Ag, Au-Au) and asymmetric (Au-Ag, Au-bathocuproine (BCP)/Ag, Au/MoO3-BCP/Ag) S-D electrodes were fabricated and their performances were investigated. The results demonstrated that the devices with asymmetric S-D electrodes are superior than their counterparts with symmetric S-D electrodes. Among the three devices with asymmetric S-D electrodes Au-BCP/Ag device exhibits the highest photo responsivity of 36.6 A/W and external quantum efficiency of 7000%, meanwhile Au-BCP/Ag and Au/MoO3-BCP/Ag device exhibit significantly larger specific detectivity than Au-Ag device. The result gives an important guideline for designing high performance OPTs.