High-Performance\nOrganic Photodetectors from a High-Bandgap Indacenodithiophene-Based\nπ‑Conjugated Donor–Acceptor Polymer

Abstract

A conjugated\ndonor–acceptor polymer, poly­[4,4,9,9-tetrakis­(4-hexylphenyl)-4,9-dihydro-<i>s</i>-indaceno­[1,2-<i>b</i>:5,6-<i>b</i>′]­dithiophene-2,7-diyl-<i>alt</i>-5-(2-ethylhexyl)-4<i>H</i>-thieno­[3,4-<i>c</i>]­pyrrole-4,6­(5<i>H</i>)-dione-1,3-diyl] (PIDT-TPD), is blended with the fullerene derivative\n[6,6]­phenyl-C61-butyric acid methyl ester (PC₆₁BM) for\nthe fabrication of thin and solution-processed organic photodetectors\n(OPDs). Systematic screening of the concentration ratio of the blend\nand the molecular weight of the polymer is performed to optimize the\nactive layer morphology and the OPD performance. The device comprising\na medium molecular weight polymer (27.0 kg/mol) in a PIDT-TPD:PC₆₁BM 1:1 ratio exhibits an external quantum efficiency of 52%\nat 610 nm, a dark current density of 1 nA/cm², a detectivity\nof 1.44 × 10¹³ Jones, and a maximum 3 dB cutoff frequency\nof 100 kHz at −5 V bias. These results are remarkable among\nthe state-of-the-art red photodetectors based on conjugated polymers.\nAs such, this work presents a functional organic active material for\nhigh-speed OPDs with a linear photoresponse at different light intensities.