Improvement of polycarbazole-based organic bulk-heterojunction solar cells using 1,8-diiodooctane

Abstract

The use of 1,8-diiodooctane (DIO) as a solvent additive in poly[N-9'-heptadecanyl-2,7-carbazole-alt-5, 5-(4',7'-di-2-thienyl-2',1',3'-benzothiadiazole)] (PCDTBT)-based bulk-heterojunction solar cells increased the power conversion efficiency (PCE) by 20.9%. This improvement was due to the increase in the fill factor and open-circuit voltage (V-oc), which compensated for the decrease in the short-circuit current (J(sc)). DIO had the opposite effect, increasing J(sc) and decreasing V-oc, in the devices using other low-band gap polymers. The best sample in this study showed a PCE of 6.27% and V-oc of 939mV, indicating that the fabricated device is an efficient solar cell with a high V-oc close to 1V. (C) 2013 AIP Publishing LLC.