Poly[3,6-bis(2-thienyl)diketopyrrolopyrrole-selenophene]: Effect of polymerization method on optical, electrochemical, and photovoltaic properties

Abstract

Diketopyrrolopyrrole-based polymers have attracted considerable interest due to their tunable electronic properties in organic electronic applications. In this work, poly[3,6-bis(2-thienyl)diketopyrrolopyrrole-selenophene] (PDPP-2 T-Se) was synthesized by two different polymerization techniques (Stille coupling and direct C-H arylation) and the effect of polymerization method on chemical and physical properties was studied. The impact of selenium atom on optical, electrical and photovoltaic properties and its comparative studies with previously reported sulfur counterpart poly[3,6-bis(2-thienyl)diketopyrrolopyrrole-thiophene] (PDPP-3 T) were also performed. Chemical and physical characterizations of these polymers were carried out using 1HNMR, FT-IR, gel permeation chromatography, UV-Vis-NIR absorption, photoluminescence, thermal gravimetric analysis, and cyclic voltammetry. Optical absorption spectra indicate that polymer has a broad absorption band from near-infrared region to visible range (950–400 nm). Photovoltaic devices were fabricated using solution-processable deposition of PDPP-2 T-Se as a donor material blended with PC71BM as an acceptor material with device structure ITO/MoOx/active layer/Al and shows a power conversion efficiency of 2.55% under ambient conditions. To get better insight into the structure-properties relationship, computational calculations were carried out on polymers PDPP-2 T-Se and PDPP-3 T.