Reduction of dark current density in organic ultraviolet photodetector by utilizing an electron blocking layer of TAPC doped with MoO3

Abstract

Abstract The work function at the surface of 4,4′Cyclohexylidenebis[N,N-bis(4-methylphenyl) benzenamine (TAPC) layer could be increased by doping MoO3 having high ionization energy. Therefore, in this work, we attempted to dope MoO3 into electron-blocking layer material of TAPC to improve the device performance of organic photodetector (OPD), which effectively suppressed dark current density and increased external quantum efficiency (EQE). When a 5% MoO3 dopant was used, the optimal OPD under reverse-biased of 3 V showed a dark current density of 1.11 nA/cm2, the EQE of 41.8% under a wavelength of 360 nm, and the detectivity of the specific wavelength surpassed 1012 Jones. In this study, we found that the decrease in the dark current density was responsible to the lower energy level of lowest unoccupied molecular orbital of TAPC and slower electron transporting capacity, which enabled the effective suppression of leakage current in OPD under bias. Furthermore, the device's EQE was substantially increased for an optimized concentration of MoO3 doped into TAPC.