Squaraine-based polymers. Toward optimized structures for optoelectronic devices

A novel polymer semiconductor based on squaric acid is successfully prepared through poly-condensation reaction. Physicochemical properties of polysquaraine are explored by Fourier transform infrared (FT-IR) and ultraviolet-visible (UV-vis) absorption spectroscopy, thermogravi-metric/modulated temperature differential scanning calorimetry (TGA/MTDSC) analyses, and cyclic voltammetry (CV). Next, the charge carrier properties are investigated through the fab-rication 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 mobili-ties (up to 5 × 10−4 cm2 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 poly-mers in field-effect transistors. Bulk heterojunction solar cells (BHJ-OSCs) are finally prepared from the blends of poly-squaraine with the fullerene derivative [6,6]-phenyl-C71-bu-tyric acid methyl ester (PC71BM). Power conversion efficiencies up to 0.86% are achieved for nonoptimized system under sim-ulated air mass 1.5 (AM1.5) conditions.