Photomultiplication type inverted organic photodetector based on PbS quantum dots

Abstract

In this paper, we report an electron injection photomultiplication (PM) type inverted organic photodetector (OPD) based on [6,6]-phenyl-C61-butyric acid methyl ester (PC61BM), poly[2,6-(4,4-bis-(2-ethylhexyl)-4H-cyclopenta[2,1-b;3,4-b’]dithiophene)-alt-4,7(2,1,3-benzothiadiazole)] (PCPDTBT), poly(3-hexylthiophene) (P3HT) and PbS quantum dots (QDs). The effects of PbS QDs added to PCPDTBT: P3HT on the optical and electrical properties of OPDs were investigated. It is found that when the mass ratio of PbS QDs is 5 wt%, the responsivity (R) and external quantum efficiency (EQE) of the device reach 15.3 A/W and 365% at −2 V bias and 430 nm illumination, respectively. The results show that PbS QDs can act as hole traps in the active layer to introduce a large amount of electron injection from the anode circuit, thereby increasing the photocurrent and realizing the PM phenomenon. However, too much doping will cause the trap material to agglomerate and fail, losing the multiplier effect. It provides a theoretical basis and method for high response polyphase inverted PM type OPDs.