Synthesis and Photovoltaic Properties of A Dithieno[6,5-b:10,11-b′]-8H-Cyclopentyl[1,2-b:4,3-b′]Diphenanthrene based Donor-Acceptor Alternating Copolymer

Abstract

A novel fused nonacyclic monomer of dithieno[6,5-b:10,11-b′]-8H-cyclopentyl[1,2-b:4,3-b′] diphenanthrene (DTCPDP) was synthesized by combining the structural features of ladder-type and multiple fused multi-cyclic aromatics. DTCPDP has a single sp3-hybridized carbon bridge between fused multi-cyclic aromatics. The copolymerization of DTCPDT with the electron accepting unit of 4,7-di(thiophen-2-yl)benzo[c][1,2,5]thiadiazole (DTBT) via Stille coupling afforded a novel donor-acceptor (D-A) alternating copolymer PDTCPDT-DTBT. The copolymer exhibited good chemical and thermal stabilities, with an optical band gap of 1.82 eV and a low-lying highest occupied molecular orbital (HOMO) energy level of -5.32 eV. When the copolymer was incorporated into polymer: fullerene (PC₇₁BM) blends to fabricate bulk heterojunction polymer solar cell devices, the devices exhibited a moderate maximum power conversion efficiency (PCE) of 5.90%.

Keywords

polymer solar cells / bulk heterojunction / ladder-type conjugated polymers

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