@article{ZhongCausaMooreetal.2020,
  author    = {Zhong, Yufei and Causa, Martina and Moore, Gareth John and Krauspe, Philipp and Xiao, Bo and G{\"u}nther, Florian and Kublitski, Jonas and BarOr, Eyal and Zhou, Erjun and Banerji, Natalie},
  title     = {Sub-picosecond charge-transfer at near-zero driving force in polymer:non-fullerene acceptor blends and bilayers},
  series = {Nature Communications},
  volume    = {11},
  journal   = {Nature Communications},
  number    = {1},
  publisher = {Nature Publishing Group UK},
  address   = {London},
  issn      = {2041-1723},
  doi       = {10.1038/s41467-020-14549-w},
  pages     = {1 -- 10},
  year      = {2020},
  abstract  = {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.},
  language  = {en}
}
@misc{ZhongCausaMooreetal.2020,
  author    = {Zhong, Yufei and Causa, Martina and Moore, Gareth John and Krauspe, Philipp and Xiao, Bo and G{\"u}nther, Florian and Kublitski, Jonas and BarOr, Eyal and Zhou, Erjun and Banerji, Natalie},
  title     = {Sub-picosecond charge-transfer at near-zero driving force in polymer:non-fullerene acceptor blends and bilayers},
  series = {Zweitver{\"o}ffentlichungen der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe},
  journal   = {Zweitver{\"o}ffentlichungen der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe},
  number    = {1},
  issn      = {1866-8372},
  doi       = {10.25932/publishup-51193},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-511936},
  pages     = {12},
  year      = {2020},
  abstract  = {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.},
  language  = {en}
}
@article{ColladoFregosoPuglieseWojciketal.2019,
  author    = {Collado-Fregoso, Elisa and Pugliese, Silvina N. and Wojcik, Mariusz and Benduhn, Johannes and Bar-Or, Eyal and Perdig{\´o}n-Toro, Lorena and H{\"o}rmann, Ulrich and Spoltore, Donato and Vandewal, Koen and Hodgkiss, Justin M. and Neher, Dieter},
  title     = {Energy-gap law for photocurrent generation in fullerene-based organic solar cells},
  series = {Journal of the American Chemical Society},
  volume    = {141},
  journal   = {Journal of the American Chemical Society},
  number    = {6},
  publisher = {American Chemical Society},
  address   = {Washington},
  issn      = {0002-7863},
  doi       = {10.1021/jacs.8b09820},
  pages     = {2329 -- 2341},
  year      = {2019},
  abstract  = {The involvement of charge-transfer (CT) states in the photogeneration and recombination of charge carriers has been an important focus of study within the organic photovoltaic community. In this work, we investigate the molecular factors determining the mechanism of photocurrent generation in low-donor-content organic solar cells, where the active layer is composed of vacuum-deposited C-60 and small amounts of organic donor molecules. We find a pronounced decline of all photovoltaic parameters with decreasing CT state energy. Using a combination of steady-state photocurrent measurements and time-delayed collection field experiments, we demonstrate that the power conversion efficiency, and more specifically, the fill factor of these devices, is mainly determined by the bias dependence of photocurrent generation. By combining these findings with the results from ultrafast transient absorption spectroscopy, we show that blends with small CT energies perform poorly because of an increased nonradiative CT state decay rate and that this decay obeys an energy-gap law. Our work challenges the common view that a large energy offset at the heterojunction and/or the presence of fullerene clusters guarantee efficient CT dissociation and rather indicates that charge generation benefits from high CT state energies through a slower decay to the ground state.},
  language  = {en}
}