Highly Sensitive Narrowband Photomultiplication-Type Organic Photodetectors Prepared by Transfer-Printed Technology

Narrowband photomultiplication-type organic photodetectors (PMOPDs) are realized with poly(3-hexylthiophene-2,5-diyl) (P3HT) as the optical field adjusting (OFA) layer and transfer-printed P3HT: [6,6]-phenyl-C-71-butyric acid methyl ester (PC71BM) (50:1, w/w) as the photomultiplication (PM) layer. The thickness of the OFA layers is adjusted to optimize interfacial trapped electron distribution and density, which determines the external quantum efficiency (EQE) and spectral response range of PMOPDs. Narrowband PMOPDs with 2.5 mu m thick P3HT as the OFA layer exhibit two narrow response peaks at 350 and 660 nm, and the corresponding EQE values at 350 and 660 nm are 180% and 760% under an applied bias of -20 V. A wide bandgap polymer poly[N,N '-bis(4-butylphenyl)-N,N '-bis(phenyl)benzidine] (P-TPD) is deliberately incorporated into OFA layer for adjusting interfacial trapped electron distribution near Al electrode. Narrowband PMOPDs exhibit only one response peak at 660 nm with the enhanced EQE value of 1120% under the same bias. The enhanced EQE of PMOPDs with P-TPD is primarily attributed to the increased hole tunneling injection and transport, which can be ascribed to the enhanced trapped electron density near the Al electrode and the improved hole mobility, respectively. Clearly resolved images can be obtained from the imaging system with the narrowband PMOPDs as sensing pixel without any current preamplifier, indicating the promising potential of PMOPDs in imaging sense.

Automated summary

Narrowband photomultiplication-type organic photodetectors (PMOPDs) were developed using poly(3-hexylthiophene-2,5-diyl) (P3HT) as the optical field adjusting (OFA) layer and transfer-printed P3HT:[6,6]-phenyl-C-71-butyric acid methyl ester (PC71BM) as the photomultiplication (PM) layer. The addition of a wide bandgap polymer poly[N,N'-bis(4-butylphenyl)-N,N'-bis(phenyl)benzidine] (P-TPD) into the OFA layer significantly enhanced the device performance, with improved hole tunneling injection and transport efficiency attributed to increased trapped electron density near the Al electrode and improved hole mobility. The promising potential of PMOPDs in imaging applications was demonstrated through clear imaging without the need for current preamplifiers.