Tuning photovoltaic performance of DOBT-based dyes via molecular design with ethynyl-linker and terminal electron-donating segment

• Published in: Dyes and pigments 2017-05, Vol.140, p.203-211
• Main Authors: Wang, Lihui, Yin, Lunxiang, Wang, Lijuan, Xie, Bao, Ji, Changyan, Li, Yanqin
• Format: Article
• Language: English
• Subjects: Benzothiadiazole; Bulk heterojunction; Carbazole; Ethynyl; Photovoltaic performance; Triphenylamine
• ISSN: 0143-7208; 1873-3743
• DOI: 10.1016/j.dyepig.2017.01.044

Two novel D-π-A-π-D-typed dioctyloxy-benzothiadiazole (DOBT)-based small molecules (SMs), TPAEDOBT and CZEDOBT, were designed and synthesized, consisting of ethynyl as π-linkage, besides, incorporating triphenylamine (TPA) and alkylated-carbazole (Cz) as terminal electron-donating units respectively. Single-bond compounds, TPADOBT and CZDOBT, were designed as references to fully investigate their photovoltaic (PV) performance of solution-processed devices. As expected, the PV properties were finely tuned via molecular design with ethynyl-linker and terminal electron-donating units. Among them, the best power conversion efficiency (PCE) of 3.21% was obtained for TPAEDOBT-based device due to triple-bond effect and high hole-mobility. Most importantly, a remarkably increased open-circuit voltage (Voc) of 1.06 V was achieved for CZEDOBT-based device due to synergistic effect of ethynyl-linker with electron-withdrawing character and Cz unit with the relatively weakened electron-donating ability, which is among the earliest report for DOBT-Cz based SMs with high Voc so far. These results provide an important guide for rational design of novel SMs PV materials. A series of novel D-π-A-π-D type DOBT-based dyes named TPAEDOBT, CZEDOBT, TPADOBT and CZDOBT have been designed and synthesized successfully for solution-processable BHJ-OSCs. Their PV properties were finely tuned via the molecular design with ethynyl-linker and terminal electron-donating units. By contrast, the relatively high PCE of 3.21% has been achieved for TPAEDOBT-based device due to its triple-bond effect and high hole-mobility capacity. Most importantly, a remarkably increased Voc of 1.06 V has been obtained for CZEDOBT-based device due to the synergistic effect of ethynyl-linker with electron-withdrawing character and Cz units with the relatively weakened electron-donating ability, which is among the earliest report for DOBT-ethynyl-Cz based SMs with high Voc so far. The results provide the valuable hints for rational design of novel SMs-donor materials. [Display omitted] •Four novel D-π-A-π-D-typed DOBT-based dyes have been synthesized for BHJ-OSCs.•PV properties were tuned via molecular design with ethynyl-bridge and terminal D unit.•A high Voc of 1.06 V was obtained for CZEDOBT due to synergistic effect of ethynyl and Cz.•A best PCE was achieved for TPAEDOBT due to triple-bond and high hole-transfer capacity.•The work provides valuable hints for rational design of novel SMs-donor materials.