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Sub-picosecond charge-transfer at near-zero driving force in polymer:non-fullerene acceptor blends and bilayers



Yufei Zhong, Martina Causa, Gareth J. Moore, Philipp Krauspe, Bo Xiao, Jonas Kublitski, Rishi Shivhare, Johannes Benduhn, Eyal BarOr, Subhrangsu Mukherjee, Kaila Yallum, Julien R?hault, Stefan C. Mannsfeld, Dieter Neher, Lee J. Richter, Dean DeLongchamp, Frank Ortmann, Koen Vandewal, Erjun Zhou, Banerji Natalie, Florian Gunther


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.
Nature Communications


Zhong, Y. , Causa, M. , Moore, G. , Krauspe, P. , Xiao, B. , Kublitski, J. , Shivhare, R. , Benduhn, J. , BarOr, E. , Mukherjee, S. , Yallum, K. , R?hault, J. , Mannsfeld, S. , Neher, D. , Richter, L. , DeLongchamp, D. , Ortmann, F. , Vandewal, K. , Zhou, E. , Natalie, B. and Gunther, F. (2020), Sub-picosecond charge-transfer at near-zero driving force in polymer:non-fullerene acceptor blends and bilayers, Nature Communications, [online],, (Accessed April 14, 2024)
Created February 10, 2020, Updated October 12, 2021