Oligo(3-hexylthiophene)-functionalized dicyano-ethylene substituted quinacridone derivatives: synthesis, characterizations and applications as acceptors in photovoltaic devices

Abstract

A series of regioregular head-to-tail oligo(3-hexylthiophene)-functionalized dicyano-ethylene substituted quinacridone derivatives DCN-Tn-QA (n = 1–3) were designed and synthesized. These linear π-conjugated donor–acceptor–donor (D–A–D) molecules with different length of the oligothiophene chain have been achieved in good yields via iterative iodination and Suzuki cross-coupling reactions followed by Knoevenagel condensations. Their photophysical and electrochemical properties, as well as density functional theory (DFT) calculations, were systematically investigated. The compounds of DCN-Tn-QA (n = 1–3) with an intense absorption range from 350–750 nm, suitable LUMO levels at around −4.0 eV and considerable film formation properties, were suitable for application in organic solar cells (OSCs) as acceptors. The organic bulk heterojunction (BHJ) solar cell based on the blend film of P3HT/DCN-T2-QA (1 : 1, w/w) (P3HT = poly(3-hexylthiophene)) showed a power conversion efficiency (PCE) of 0.51% under the illumination of AM.1.5, 100 mW cm⁻². Compared with P3HT/PCBM (PCBM = [6,6]-phenyl-C61-butyric acid methyl ester), the blend film of P3HT/DCN-T2-QA displayed a stronger response to the solar spectrum in the long wavelength range from 665–750 nm.