Significant enhancement of photodetector performance by subtle changes in the side chains of dithienopyrrole-based polymers

Abstract

A pair of analogous polymers based on diketopyrrolopyrrole (DPP) and dithienopyrrole (DTP) were designed to have a small structural difference in the side chain, PDDPDTP-C with an alkyl chain and PDPPDTP-P with an alkylphenyl chain. The two polymers have the same absorption and band gap but show different hole mobility, molecular stacking and film morphology. As a result, the PDPPDTP-P photodetector has a much higher responsivity (291 mA W⁻¹ at 900 nm at −0.1 V) than the one based on PDDPDTP-C (36 mA W⁻¹), and exhibits a specific detectivity over 10¹² Jones in the spectral region of 350–950 nm.