Asymmetric, efficient π-conjugated organic semiconducting chromophore for bulk-heterojunction organic photovoltaics

A novel, asymmetric benzothiadiazole-core π-conjugated organic semiconducting chromophore (CF-BTz-ThR) containing an alkyl bithiophene donor and 3,5-bis (trifluoromethyl) benzene as acceptor unit was synthesized via Suzuki cross-coupling in a relatively cost-effective way. The synthesized chromophore was applied as an acceptor material in the solution-processed fabrication of bulk heterojunction (BHJ) organic photovoltaics (OPVs). The presence of terminal hexyl chain in CF-BTz-ThR induced its solubility in common organic solvents. The energy levels of CF-BTz-ThR were calculated as −5.22 eV and −3.19 eV for HOMO and LUMO, respectively. The fabricated devices attained power conversion efficiency (PCE) of ∼3.52% for CF-BTz-ThR: PC61BM (1:3, w/w) ratio with the short circuit current (JSC) of ∼10.38 mA/cm2 and the open-circuit voltage (VOC) of ∼0.68 V. The reasonable JSC and VOC of the devices might be attributed to strong absorption and emission properties as well as the electrochemical properties due to the presence of strong electron-withdrawing benzothiadiazole as well as -CF3 unit as electron-acceptor.