Department of Chemistry, Faculty of Science, Alexandria University, Alexandria 21321, Egypt.
Department of Chemistry, College of Sciences, Taibah University, Yanbu 56423, Saudi Arabia.
J Chem Inf Model. 2021 Oct 25;61(10):5098-5116. doi: 10.1021/acs.jcim.1c00739. Epub 2021 Sep 29.
Cosensitization of the semiconducting electrode in dye-sensitized solar cells (DSCs), with two or more light-harvesting dyes, is a chemical fabrication method that aims to achieve a panchromatic absorption spectrum emulating that of the solar emission spectrum. In this paper, SQ02 and BP-2 cosensitizers have been investigated, as isolated monomers/dimer and adsorbed monomers/dimer on the TiO (101) anatase surface, by employing density functional theory (DFT) and time-dependent DFT calculations. Computed results showed that the dominant electron injection pathway is direct injection from each dye into the conduction band of TiO. The almost complete spectral overlap between the simulated absorption spectrum of BP-2 and fluorescence emissions of SQ02 implies that excitation energy transfer occurs between cosensitizers via the trivial reabsorption mechanism. However, the results showed very limited unidirectional intermolecular charge transfer (CT) from SQ02 dye to BP-2 dye (0.04 |e|). Therefore, this study also presents a stepwise molecular engineering of BP-2 dye, aiming at optimizing the cosensitization functionality. First, 14 redesigned dye candidates are reported to identify dyes with photophysical properties matching the requirements for efficient DSCs. Second, the four most promising dyes are shortlisted for testing as cosensitizers with the SQ02 dye. The molecular design factors of cosensitization that need validation are chemical compatibility, availability of CT between cosensitizers, and complementarity of the absorption spectra. This screening suggests the judicious choice of the modeled difluorenyl amine donor-based dye (BP-D4) as a very promising cosensitizer. In particular, the SQ02/BP-D4 dimer showed 10 times larger (0.53 |e|) unidirectional CT than that of SQ02/BP-2 dimer, in addition to the maximum increased electron population of acceptor moieties upon photoexcitation.
染料敏化太阳能电池 (DSC) 中半导体电极的共敏化作用，使用两种或更多种光捕获染料，是一种旨在实现模拟太阳发射光谱的全色吸收光谱的化学制造方法。在本文中，通过使用密度泛函理论 (DFT) 和含时密度泛函理论 (TD-DFT) 计算，研究了 SQ02 和 BP-2 共敏化剂作为孤立单体/二聚体和吸附在 TiO(101)锐钛矿表面上的单体/二聚体。计算结果表明，主导的电子注入途径是每个染料直接注入 TiO 的导带。BP-2 的模拟吸收光谱与 SQ02 的荧光发射之间几乎完全的光谱重叠表明，共敏化剂之间通过平凡的再吸收机制发生了激发能量转移。然而，结果表明，SQ02 染料向 BP-2 染料的单向分子间电荷转移 (CT) 非常有限 (0.04 |e|)。因此，本研究还提出了 BP-2 染料的逐步分子工程，旨在优化共敏化功能。首先，报告了 14 种重新设计的染料候选物，以鉴定具有满足高效 DSCs 要求的光物理性质的染料。其次，筛选出四种最有前途的染料作为 SQ02 染料的共敏化剂进行测试。需要验证的共敏化分子设计因素包括化学相容性、共敏化剂之间 CT 的可用性以及吸收光谱的互补性。该筛选表明，基于二氟苯并噻二唑供体的模型染料 (BP-D4) 是一种非常有前途的共敏化剂的明智选择。特别是，SQ02/BP-D4 二聚体的单向 CT 比 SQ02/BP-2 二聚体大 10 倍 (0.53 |e|)，此外，光激发后受体部分的电子占据数也最大增加。
