Squaraine-Based Polymers: Toward Optimized Structures for Optoelectronic Devices

A novel polymer semiconductor based on squaric acid is successfully prepared through polycondensation reaction. Physicochemical properties of polysquaraine are explored by Fourier transform infrared (FT-IR) and ultraviolet-visible (UV-vis) absorption spectroscopy, thermogravimetric/modulated temperature differential scanning calorimetry (TGA/MTDSC) analyses, and cyclic voltammetry (CV). Next, the charge carrier properties are investigated through the fabrication and characterization of field-effect transistors (FETs) using solution-processed polymeric films. It is found that the polysquaraine is FET active and exhibits decent p-type mobilities (up to 5 x 10(-4) cm(2) V-1 s(-1)), which illustrates the promising properties of this semiconductor in optoelectronics. Notably, there is no precedent for the use of squaraine-based polymers in field-effect transistors. Bulk heterojunction solar cells (BHJ-OSCs) are finally prepared from the blends of polysquaraine with the fullerene derivative [6,6]-phenyl-C-71-butyric acid methyl ester (PC71BM). Power conversion efficiencies up to 0.86% are achieved for nonoptimized system under simulated air mass 1.5 (AM1.5) conditions.