Photomultiplication (PM) type organic photodetectors (OPDs) based on electron tunneling injection are achieved with a specific structure of ITO/ZnO/PC₇₁BM:P3HT (100 : 5, wt/wt)/Au and can work well under forward and reverse bias. A rather low dark current density of the PM type OPDs is obtained due to the large electron injection barrier of 0.7 eV from the ITO electrode or 1.1 eV from the Au electrode, as well as the absence of continuous hole transport channels in the active layers. The external quantum efficiency (EQE) spectral shape of PM type OPDs can be easily adjusted by altering the bias polarity and active layer thickness, which can be well explained by the trapped hole distribution near the ITO and Au electrodes, respectively. The PM type OPDs with 400 nm active layers exhibit the maximum EQE of 3900% and 4900% under 5 V and −5 V bias, respectively. This work firstly achieves PM type OPDs with electron-only transport properties, which has great potential to well match with other organic electronic devices.

UV-Vis-NIR broad-band organic photomultiplication-type photodetectors (OPMPDs) were fabricated with a device structure of indium tin oxide (ITO)/zinc oxide (ZnO)/(∼150 nm) active layers/Au. The active layers consisted of a 2,2′-((2Z,2′Z)-((12,13-bis(2-ethylhexyl)-3-undecyl-9-(undecyloxy)-12,13-dihydro-[1,2,5]thiadiazolo[3,4-e]thieno[2′′,3′′:4′,5′]thieno[2′,3′:4,5]pyrrolo[3,2-g]thieno[3,2-b]indole-2,10-diyl)bis(methaneylylidene))bis(5,6-difluoro-3-oxo-2,3-dihydro-1H,1-diylidene))dimalononitrile (Y6-1O):5-(5-(4,8-bis(4-chloro-5-(2-ethylhexyl)thiophen-2-yl)-6-methylbenzo[1,2-b:4,5-b′]dithiophen-2-yl)-4-(2-butyloctyl)-2-yl)-8-(4-(2-butyloctyl)-5-thiophen-2-yl)dithieno[3′,2′:3,4;2′′,3′′:5,6]benzo[1,2-c][1,2,5]thiadiazole (D18-Cl) (1.6 : 1, wt/wt) layer determining the spectral response range and one photomultiplication (PM) layer [6,6]-phenyl-C71-butyric acid methyl ester (PC₇₁BM):poly(3-hexylthiophene-2,5-diyl) (P3HT) (100 : 5, wt/wt). The spectral response of the double-layered OPMPDs was determined by the trapped-hole distribution in PC₇₁BM:P3HT near by Au electrode, which mainly originated from the photogenerated hole in the Y6-1O:D18-Cl layer. The trapped-hole in P3HT induced interfacial band-bending for efficient electron-tunneling injection from the Au electrode. The trapped-hole-induced electron-tunneling injection could be markedly enhanced by increasing the applied voltage, leading to markedly improved external quantum efficiency (EQE) values. The double-layered OPMPDs exhibited a broad spectral response range from 300 to 1000 nm, and achieved a highly effective EQE of approximately 50 400% at 360 nm under an applied voltage of 5 V, which was the highest value among organic photodetectors (OPDs) under the same applied voltage. Moreover, the maximum specific detectivity (D*) of 3 × 10¹² jones and a linear dynamic range (LDR) of 120 dB at 810 nm under an applied voltage of 5 V were achieved in the double-layered OPMPDs. This study brings forward a smart strategy to achieve high performance broad-band OPMPDs by employing double-layered thin active layers.