Wu ZhiFang, Li Xin, Li Jing, Hua JianLi, Agren Hans, Tian He
Key Laboratory for Advanced Materials, Institute of Fine Chemicals, East China University of Science and Technology, Shanghai 200237 (China), Fax: (+86) -264252756.
Chem Asian J. 2014 Dec;9(12):3549-57. doi: 10.1002/asia.201402608. Epub 2014 Sep 15.
Three new dyes with a 2-(1,1-dicyanomethylene)rhodanine (IDR-I, -II, -III) electron acceptor as anchor were synthesized and applied to dye-sensitized solar cells. We varied the bridging molecule to fine tune the electronic and optical properties of the dyes. It was demonstrated that incorporation of auxiliary acceptors effectively increased the molar extinction coefficient and extended the absorption spectra to the near-infrared (NIR) region. Introduction of 2,1,3-benzothiadiazole (BTD) improved the performance by nearly 50 %. The best performance of the dye-sensitized solar cells (DSSCs) based on IDR-II reached 8.53 % (short-circuit current density (Jsc)=16.73 mA cm(-2), open-circuit voltage (Voc)=0.71 V, fill factor (FF)=71.26 %) at AM 1.5 simulated sunlight. However, substitution of BTD with a group that featured the more strongly electron-withdrawing thiadiazolo[3,4-c]pyridine (PT) had a negative effect on the photovoltaic performance, in which IDR-III-based DSSCs showed the lowest efficiency of 4.02 %. We speculate that the stronger auxiliary acceptor acts as an electron trap, which might result in fast combination or hamper the electron transfer from donor to acceptor. This inference was confirmed by electrical impedance analysis and theoretical computations. Theoretical analysis indicates that the LUMO of IDR-III is mainly localized at the central acceptor group owing to its strong electron-withdrawing character, which might in turn trap the electron or hamper the electron transfer from donor to acceptor, thereby finally decreasing the efficiency of electron injection into a TiO2 semiconductor. This result inspired us to select moderated auxiliary acceptors to improve the performance in our further study.
合成了三种以2-(1,1-二氰基亚甲基)罗丹宁（IDR-I、-II、-III）电子受体为锚定基团的新型染料，并将其应用于染料敏化太阳能电池。我们改变桥连分子以微调染料的电子和光学性质。结果表明，引入辅助受体有效地提高了摩尔消光系数，并将吸收光谱扩展到近红外（NIR）区域。引入2,1,3-苯并噻二唑（BTD）使性能提高了近50%。基于IDR-II的染料敏化太阳能电池（DSSC）在AM 1.5模拟太阳光下的最佳性能达到8.53%（短路电流密度（Jsc）=16.73 mA cm(-2)，开路电压（Voc）=0.71 V，填充因子（FF）=71.26%）。然而，用具有更强吸电子性的噻二唑并[3,4-c]吡啶（PT）基团取代BTD对光伏性能产生了负面影响，其中基于IDR-III的DSSC效率最低，为4.02%。我们推测，更强的辅助受体充当电子陷阱，这可能导致快速复合或阻碍电子从供体转移到受体。电阻抗分析和理论计算证实了这一推断。理论分析表明，由于IDR-III的强吸电子特性，其最低未占分子轨道（LUMO）主要定域在中心受体基团上，这可能反过来捕获电子或阻碍电子从供体转移到受体，从而最终降低电子注入TiO2半导体的效率。这一结果促使我们在进一步的研究中选择适度的辅助受体来提高性能。
