Highly sensitive polymer photodetectors with a wide spectral response range

A series of highly sensitive polymer photodetectors (PPDs) was fabricated with P3HT(100-x): PBDT-TS1(x): PC71BM1 as the active layers, where x represents the PBDT-TS1 doping weight ratio in donors. The response range of PPDs can cover from the UV to near-infrared regions by adjusting the PBDT-TS1 doping weight ratio. The best external quantum efficiency (EQE) values of ternary PPDs with P3HT: PBDT-TS1: PC71BM (50: 50: 1 wt/wt/wt) as the active layers reach 830%, 720%, and 330% under 390-, 625-, and 760-nm light illumination and 10 V bias, respectively. The large EQE values indicate that the photodetectors utilise photomultiplication (PM). The working mechanism of PM-type PPDs can be attributed to interfacial trap-assisted hole tunnelling injection from the external circuit under light illumination. The calculated optical field and photogenerated electron volume density in the active layers can well explain the EQE spectral shape as a function of the PBDT-TS1 doping weight ratio in donors.