Effect of organic electron blocking layers on the performance of organic photodetectors with high ultraviolet detectivity

The performance of organic ultraviolet photodetectors (UV-PDs) was investigated by focusing on the role of N,N'-bis-(1-naphthyl)-N,N'-diphenyl-1,1'-biphenyl-4,4'-diamine (NPB), N,N'-diphenyl-N,N'-bis(3-methyllphenyl)-(1,1'-biphenyl)-4,4'-diamine (TPD), 1,1-bis((di-4-tolylamino)-phenyl) cyclohexane (TAPC), and 4,4,4-tri(N-carbazolyl) triphenylamine) (TCTA) as the electron blocking layers (EBLs). The results showed that the UV-PDs with different EBLs exhibited significant improved electrical characteristics, such as dark current, detectivity and on/off ratio. Moreover, by analyzing the dark current behavior, it was also found that the EBLs can effectively suppress the charge carrier injection from Ag/MoO3 electrode to the active layer. In addition, through optimizing the film thickness of EBL, a high detectivity of 5.59 × 1012 Jones by 4.53 folds enhancement was achieved.