Perrella Fulvio, Li Xiaosong, Petrone Alessio, Rega Nadia
Department of Chemical Sciences, University of Napoli Federico II, Complesso Universitario di M.S. Angelo, via Cintia 21, I-80126 Napoli, Italy.
Department of Chemistry, University of Washington, Seattle, Washington 98195, United States.
JACS Au. 2022 Dec 15;3(1):70-79. doi: 10.1021/jacsau.2c00556. eCollection 2023 Jan 23.
Charge-transfer dynamics and interligand electron transfer (ILET) phenomena play a pivotal role in dye-sensitizers, mostly represented by the Ru-based polypyridyl complexes, for TiO and ZnO-based solar cells. Starting from metal-to-ligand charge-transfer (MLCT) excited states, charge dynamics and ILET can influence the overall device efficiency. In this letter, we focus on N3 dye ( [Ru(dcbpy)(NCS)], dcbpy = 4,4'-dicarboxy-2,2'-bipyridine) to provide a first direct observation with high time resolution (<20 fs) of the ultrafast electron exchange between bpy-like ligands. ILET is observed in water solution after photoexcitation in the ∼400 nm MLCT band, and assessment of its ultrafast time-scale is here given through a real-time electronic dynamics simulation on the basis of state-of-the-art electronic structure methods. Indirect effects of water at finite temperature are also disentangled by investigating the system in a symmetric gas-phase structure. As main result, remarkably, the ILET mechanism appears to be based upon a purely electronic evolution among the dense, experimentally accessible, MLCT excited states manifold at ∼400 nm, which rules out nuclear-electronic couplings and proves further the importance of the dense electronic manifold in improving the efficiency of dye sensitizers in solar cell devices.
电荷转移动力学和配体间电子转移（ILET）现象在染料敏化剂中起着关键作用，这些染料敏化剂主要以钌基多吡啶配合物为代表，用于基于TiO和ZnO的太阳能电池。从金属到配体的电荷转移（MLCT）激发态开始，电荷动力学和ILET会影响整个器件的效率。在这封信中，我们聚焦于N3染料（[Ru(dcbpy)(NCS)]，dcbpy = 4,4'-二羧基-2,2'-联吡啶），以首次在高时间分辨率（<20 fs）下直接观察类联吡啶配体之间的超快电子交换。在约400 nm的MLCT波段光激发后，在水溶液中观察到ILET，并在此通过基于最先进电子结构方法的实时电子动力学模拟对其超快时间尺度进行评估。通过研究对称气相结构中的体系，还解开了有限温度下水的间接影响。作为主要结果，值得注意的是ILET机制似乎基于约400 nm处密集的、实验上可及的MLCT激发态多重态之间的纯电子演化，这排除了核 - 电子耦合，并进一步证明了密集电子多重态在提高太阳能电池器件中染料敏化剂效率方面的重要性。
