Zhong Yufei, Causa' Martina, Moore Gareth John, Krauspe Philipp, Xiao Bo, Günther Florian, Kublitski Jonas, Shivhare Rishi, Benduhn Johannes, BarOr Eyal, Mukherjee Subhrangsu, Yallum Kaila M, Réhault Julien, Mannsfeld Stefan C B, Neher Dieter, Richter Lee J, DeLongchamp Dean M, Ortmann Frank, Vandewal Koen, Zhou Erjun, Banerji Natalie
Department of Chemistry and Biochemistry, University of Bern, Freiestrasse 3, CH-3012, Bern, Switzerland.
Chinese Academy of Sciences (CAS) Key Laboratory of Nanosystem and Hierarchical Fabrication, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology, Beijing, 100190, P. R. China.
Nat Commun. 2020 Feb 11;11(1):833. doi: 10.1038/s41467-020-14549-w.
Organic photovoltaics based on non-fullerene acceptors (NFAs) show record efficiency of 16 to 17% and increased photovoltage owing to the low driving force for interfacial charge-transfer. However, the low driving force potentially slows down charge generation, leading to a tradeoff between voltage and current. Here, we disentangle the intrinsic charge-transfer rates from morphology-dependent exciton diffusion for a series of polymer:NFA systems. Moreover, we establish the influence of the interfacial energetics on the electron and hole transfer rates separately. We demonstrate that charge-transfer timescales remain at a few hundred femtoseconds even at near-zero driving force, which is consistent with the rates predicted by Marcus theory in the normal region, at moderate electronic coupling and at low re-organization energy. Thus, in the design of highly efficient devices, the energy offset at the donor:acceptor interface can be minimized without jeopardizing the charge-transfer rate and without concerns about a current-voltage tradeoff.
基于非富勒烯受体（NFA）的有机光伏器件展现出16%至17%的创纪录效率，且由于界面电荷转移的驱动力较低，光电压有所提高。然而，低驱动力可能会减缓电荷产生，导致电压与电流之间的权衡。在此，我们针对一系列聚合物：NFA体系，将本征电荷转移速率与形态依赖的激子扩散区分开来。此外，我们分别确定了界面能量学对电子和空穴转移速率的影响。我们证明，即使在接近零驱动力的情况下，电荷转移时间尺度仍保持在几百飞秒，这与Marcus理论在正常区域、适度电子耦合和低重组能情况下预测的速率一致。因此，在高效器件的设计中，施主：受主界面处的能量偏移可以最小化，而不会危及电荷转移速率，也无需担心电流-电压权衡问题。
