Enhanced performance of near infrared and broad spectral response organic photodiodes exploiting NPB as electron blocking layer

摘要

Near infrared (NIR) and broad spectral (BS) responsive organic photodiodes (OPDs) have broad application prospects because of their unique characteristics. In order to fabricate excellent devices, suppressing dark currents under reverse bias is a key indicator to improve the performance of OPDs. Here we report a NIR-OPD and a BS-OPD exploiting NPB as electron blocking layer which can effectively suppressed the dark current of the devices. For the NIR-OPD, a decrease of 61% for the dark current has achieved at an optimized NPB thickness of 10 nm, and the performance are improved accordingly. Compare with no NPB device, the photoresponsivity (R), specific detectivity (D*) and external quantum efficiency (EQE) increase probably 25%, 100% and 25% under 780 nm wavelength irradiation, respectively. For the BS-OPD, the effects of the mixture ratio of the SnPc:PTCDA bulk heterojunction has been investigated, where SnPc denotes Tin(II) phthalocyanine and PTCDA denotes 3,4,9,10-perylenete-acarboxylic dianhydride. The results show that at the ratio of 3:2, the photo responsivity is maximal. At this optimized mixture ratio, the R, D* and EQE of the device improved at least 250%, 61% and 78%, respectively.