Prato reaction derived polythiophene/C60 donor–acceptor double cable polymer, fabrication of photodetectors and evaluation of photocurrent generation

Abstract

Herein, a side chain engineered polythiophene copolymer based organic semiconductor polymer (OSP) with pendant aldehyde groups was synthesized by a combination of Grignard Metathesis (GRIM) polymerization and post-synthetic modifications. The pendant aldehyde groups of OSP (electron donor-D) were covalently conjugated to the pristine C₆₀ (elector acceptor-A) via 1,3-dipolar cycloaddition reaction (i.e., Prato reaction) between the pristine C₆₀ and azomethine ylide formed in situ as a result of the reaction of pendant aldehyde groups and sarcosine. The OSP with pendant aldehyde groups and its covalent conjugate with pristine C₆₀ were fully characterized using FTIR and ¹H-NMR spectroscopies. Fluorescence spectroscopic analysis of the synthesized D–A double cable covalent hybrid and physical hybrid derived from the physical mixing of the synthesized OSP and C₆₀ revealed a higher fluorescence quenching in the case of the covalent hybrid. This novel precisely designed D–A hybrid material was employed as the photoactive layer in an interdigitated gold electrode based photodetector where a significant enhancement in photocurrent (>2.5 times) was observed in the devices consisting of photoactive layer derived from the D–A covalent hybrid. This work offers a step forward in the systematic development of D–A covalent hybrids with a precise molecular design to fabricate efficient photovoltaic devices.