A novel carbazole-based dye outperformed the benchmark dye N719 for high efficiency dye-sensitized solar cells (DSSCs)
作者:Ahmed El-Shafei、Maqbool Hussain、Aasim Atiq、Ashraful Islam、Liyuan Han
DOI:10.1039/c2jm35267b
日期:——
Two novel high molar extinction coefficient heteroleptic Ru(II) isomers, NCSU-10 and NCSU-10′, based on carbazole antenna were synthesized with the aid of Knoevenagel reaction, to study the influence of the carbazole antenna and anchoring group (COOH) isomerization on the light harvesting efficiency (LHE), ground and excited state oxidation potentials, incident-photon-to-current conversion efficiency (IPCE), short-circuit photocurrent density (JSC), and total solar-to-electric conversion efficiency (η) for DSSCs, and their device performances were compared to the benchmark dye N719. The photophysical and photoelectrochemical properties discussed herein addressed the significant impact of the carbazole antenna and the position of the anchoring group on JSC and η in DSSCs. Tetrabutylammonium (TBA) substituted NCSU-10 achieved efficient sensitization of nanocrystalline TiO2 over the whole visible range, extending into the near IR region (ca. 870 nm) with an excellent power conversion efficiency (η) of 9.37% under an irradiation of full sunlight (100 mW cm−2) with mask compared to 8.17% of N719 under optimized conditions. NCSU-10 outperformed N719 by 45% in molar absorptivity, 18.8% in JSC, and 14.6% in the total conversion efficiency. Molecular modeling studies (DFT/TD-DFT) of NCSU-10 and NCSU-10′ showed that the HOMO is delocalized not only on Ru and NCS but also on the carbazole with a large coefficient, indicating that the second charge generation transfer in the visible region at ∼400 nm is a mixture of metal-to-ligand charge transfer (MLCT) and strong ligand–ligand charge transfer (LLCT) with a significant HOMO coefficient originating from the carbazole antenna (π) to the bipyridyl electron acceptor (π*). Moreover, DFT calculations showed that the 4,4′-isomer (NCSU-10) is a significantly stronger electron acceptor than the 5,5′-isomer (NCSU-10′), which explained the inferior electron injection and significantly lower JSC of the 5,5′-isomer.
借助Knoevenagel反应合成了两种基于咔唑天线的新型高摩尔消光系数杂配Ru(II)异构体NCSU-10和NCSU-10',研究了咔唑天线和锚定基团(COOH)异构化的影响光捕获效率(LHE)、基态和激发态氧化电位、入射光子到电流的转换效率(IPCE)、短路光电流密度(JSC)和总太阳能到电能的转换效率(η) DSSC 的器件性能与基准染料 N719 进行了比较。本文讨论的光物理和光电化学性质解决了咔唑天线和锚定基团位置对 DSSC 中 JSC 和 η 的显着影响。四丁基铵(TBA)取代的NCSU-10在整个可见光范围内实现了纳米晶TiO2的高效敏化,延伸到近红外区域(约870 nm),在全阳光照射下具有9.37%的优异功率转换效率(η) (100 mW cm−2) 与优化条件下 N719 的 8.17% 相比,使用掩模。 NCSU-10 的摩尔吸收率比 N719 高 45%,JSC 比 N719 高 18.8%,总转换效率比 N719 高 14.6%。 NCSU-10和NCSU-10′的分子模型研究(DFT/TD-DFT)表明HOMO不仅在Ru和NCS上离域,而且在咔唑上也有很大的离域系数,表明第二次电荷产生转移〜400 nm的可见光区域是金属到配体电荷转移(MLCT)和强配体-配体电荷转移(LLCT)的混合物,具有源自咔唑天线(π)到联吡啶电子受体(π)的显着HOMO系数*)。此外,DFT计算表明,4,4'-异构体(NCSU-10)的电子受体明显强于5,5'-异构体(NCSU-10'),这解释了电子注入较差和JSC显着降低的原因。 5,5′-异构体。