Realizing high detectivity organic photodetectors in visible wavelength by doping highly ordered polymer PCPDTBT

A new method for realizing the response broadening of organic photodetectors (OPDs) using highly ordered polymer PCPDTBT doping has been proposed in this paper. The effects of PCPDTBT doping on the optical and electrical properties of OPDs were investigated experimentally. It was found that when the mass ratio of PTB7:PCPDTBT:PC61BM was 8.5:1.5:15, the response spectrum of the OPDs was broadened to 380–830 nm. The responsivity (R) and external quantum efficiency (EQE) of the OPDs reached 396, 244, 189 mA/W and 78%, 57%, 51% under 630, 530 and 460 nm illumination and −1 V bias, respectively, and the detectivity (D*) reached 1011 Jones. The results showed that the addition of PCPDTBT to PTB7:PC61BM increased the absorption of light at 700–830 nm. At the same time, the addition of PCPDTBT promotes the exciton dissociation interface in the active layer from the original one to the current three, they are PTB7:PCPDTBT, PTB7:PC61BM and PCPDTBT:PC61BM, which increase the probability of exciton dissociation in the active layer. In addition, the addition of highly ordered polymer PCPDTBT promotes the crystallization of the film and optimizes the carrier transport of the film. These synergistic effects promote the photocurrent of the OPDs.