Long-range exciton diffusion in molecular non-fullerene acceptors

Yuliar Firdaus(King Abdullah University of Science and Technology), Vincent M. Le Corre(University of Groningen), Safakath Karuthedath(King Abdullah University of Science and Technology), Wenlan Liu(Max Planck Institute for Polymer Research), Anastasia Markina(Max Planck Institute for Polymer Research), Wentao Huang(Imperial College London), Shirsopratim Chattopadhyay(Oregon State University), Masrur Morshed Nahid(North Carolina State University), Mohamad Insan Nugraha(King Abdullah University of Science and Technology), Yuanbao Lin(King Abdullah University of Science and Technology), Akmaral Seitkhan(King Abdullah University of Science and Technology), Aniruddha Basu(King Abdullah University of Science and Technology), Weimin Zhang(King Abdullah University of Science and Technology), Iain McCulloch(King Abdullah University of Science and Technology), Harald Ade(North Carolina State University), John G. Labram(Oregon State University), Frédéric Laquai(King Abdullah University of Science and Technology), Denis Andrienko(Max Planck Institute for Polymer Research), L. Jan Anton Koster(University of Groningen), Thomas D. Anthopoulos(King Abdullah University of Science and Technology)
Nature Communications
October 15, 2020
10.1038/s41467-020-19029-9
Cited by 379Open Access
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Abstract

The short exciton diffusion length associated with most classical organic semiconductors used in organic photovoltaics (5-20 nm) imposes severe limits on the maximum size of the donor and acceptor domains within the photoactive layer of the cell. Identifying materials that are able to transport excitons over longer distances can help advancing our understanding and lead to solar cells with higher efficiency. Here, we measure the exciton diffusion length in a wide range of nonfullerene acceptor molecules using two different experimental techniques based on photocurrent and ultrafast spectroscopy measurements. The acceptors exhibit balanced ambipolar charge transport and surprisingly long exciton diffusion lengths in the range of 20 to 47 nm. With the aid of quantum-chemical calculations, we are able to rationalize the exciton dynamics and draw basic chemical design rules, particularly on the importance of the end-group substituent on the crystal packing of nonfullerene acceptors.

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