Photomultiplication type organic photodetectors with tunable spectral response range

Photomultiplication (PM) type organic photodetectors (OPDs) with two detection windows were fabricated with a specific structure of ITO/PDIN/active layers/semitransparent Al, only holes can be transported in the active layers with 100:1 wt ratio of P3HT to PC61BM. The specific structure makes the PM type OPDs working under top/bottom light illumination and forward/reverse bias conditions, exhibiting a tunable spectral response range. The rather less PC61BM may prefer to be surrounded by P3HT to form some isolated electron traps in the active layers, which is beneficial to decreasing the dark current density (J(D)) of OPDs with hole-only transport channels provided by P3HT. Under dark condition, holes are hardly injected from ITO/PDIN or Al electrode to the highest occupied molecular orbits (HOMO) of P3HT due to the large interfacial injection barriers, resulting in the rather low J(D). Holes can be easily injected from electrodes due to the trap-assisted interfacial band bending under light illumination conditions. The external quantum efficiency (EQE) spectra of PM type OPDs are determined by the photogenerated electron distribution on the cross-section near electrode, which can be well supported by the corresponding simulation results based on transfer matrix method. The PM type OPDs integrated with two detection windows exhibit broadband and narrowband response range under forward or reverse bias, which should have great potential in the integrated optoelectronic products, especially in the field of artificial intelligence.