Photoelectronic multiplication organic photodetectors with facile fabrication and controllable operating voltage

Abstract

Abstract Organic photodetectors (OPDs) possessing high responsivity are promising building blocks for exploring good performance integrated optoelectronics products. Herein, photoelectronic multiplication (PM) type OPDs are fabricated by doping small ratio C60 as electron traps into PBDT-TT-F:PC61BM bulk heterojunction (BHJ). The mechanism of PM assisted by C60 is analyzed systematically, especially for the influence of C60 concentration on the device performance. For obtaining an ideal operating voltage of required OPDs, we further change the PC61BM concentration to adjust the voltage happening tunneling injection. On the basis, the PM type OPD with low bias and facile fabrication is achieved where the optimized weight ratio of PBDT-TT-F:PC61BM:C60 is 6:6:0.2. The EQE spectra of the resulting OPD shows broadband response and >100% EQE values in visible region under reverse bias. At −3.0 V bias, they arrive to 629.1%, 655.7%, and 739.8% under the illumination of three selected wavelengths of 460, 530, and 630 nm, respectively. The experimental results indicate that the effective electron traps can be formed by introducing a small weight of C60 into the active layer. Moreover, the observed >100% EQE values are attributed to the cathode hole tunneling injection assisted by the trapped electrons in C60 near the Al cathode. The present study provides theoretical basis and method to obtain the desirable operating voltage of PM type OPDs with facile fabrication.