Novel branched coumarin dyes for dye-sensitized solar cells: significant improvement in photovoltaic performance by simple structure modification
作者:Bo Liu、Ran Wang、Weijun Mi、Xiaoyan Li、Haitao Yu
DOI:10.1039/c2jm32333h
日期:——
The construction of branched coumarin dyes based on a 2D-π-A system is focused to optimize the light-harvesting capability and enhance the photovoltaic performance. Three novel coumarin dyes, coded as MS-C, MS-F, and MS-M, respectively, were obtained by incorporating different units (carbazole, fluorene and methyl groups) with different molecular volume and degrees of electron-donating capability into the π-conjugation linker. Through molecular engineering, their light-harvesting capabilities, energy levels and photovoltaic performance were studied systematically. As expected, with the additional donor, especially utilizing strong electron-donating carbazole unit, the IPCE action spectrum of MS-C keeps a high plateau from 390 nm to 580 nm with nearly unity values. Along with the improvement of IPCE, the Jsc values of the three dyes were increased by 77% from 7.61 (MS-M) to 13.47 mA cm−2 (MS-C). Using DCA as the co-adsorbed material, the Jsc of MS-M was increased while these values were decreased in the cases of branched MS-C and MS-F. This means that the twist structure arising from the branched donors could prevent π-aggregation effectively. More importantly, the Voc was also improved significantly by introducing the additional donor. While the branched 2D-π-A system was constructed, the Voc was sharply increased from 508 (MS-M) to 610 mV (MS-C). Comprehensively, a more than 100% enhancement in overall conversion efficiency (5.53%) was realized by branched MS-C compared to the linear MS-M (2.74%). Although the overall conversion efficiencies of these dyes are not very high, these results will still afford significant value for future development of efficient coumarin sensitizers with high open-circuit voltage.
基于2D-π-A系统的分支香豆素染料的构建旨在优化光捕获能力并提升光伏性能。通过将不同单元(卡巴佐、氟烯和甲基)与具有不同分子体积和电子供给能力的π共轭连结体结合,获得了三种新型香豆素染料,分别编码为MS-C、MS-F和MS-M。通过分子工程,系统性地研究了它们的光捕获能力、能级和光伏性能。如预期所示,随着额外供体的引入,特别是利用强电子供体卡巴佐单元,MS-C的IPCE作用谱在390 nm至580 nm范围内保持高平台,值接近于1。随着IPCE的提高,三种染料的短路电流密度(Jsc)值从7.61 mA cm−2(MS-M)增加到13.47 mA cm−2(MS-C),增加幅度达到77%。使用DCA作为共吸附材料时,MS-M的Jsc有所增加,而分支的MS-C和MS-F的值则有所下降。这意味着源于分支供体的扭曲结构可以有效防止π聚集。更重要的是,通过引入额外的供体,开路电压(Voc)得到了显著提升。当构建分支的2D-π-A系统时,Voc从508 mV(MS-M)急剧增加到610 mV(MS-C)。综合来看,与线性MS-M(2.74%)相比,分支的MS-C在总体转换效率上实现了超过100%的提升(5.53%)。尽管这些染料的总体转换效率并不非常高,但这些结果仍将对未来开发高开路电压的高效香豆素敏化剂提供重要价值。