High-Efficiency Organic Solar Cells Based on Polymer Donors: The Impact of Non-Fullerene Acceptors*

With the emergence of efficient non-fullerene acceptors some five years ago, the power conversion efficiency of organic solar cells (OSCs) has increased remarkably, from some 12% to over 18%. In OSCs, the active layers consist of bulk-heterojunctions, that is blends of an electron donor component, usually a π-conjugated polymer, and an electron acceptor component. The inter-molecular charge-transfer (CT) electronic states that appear at the donor-acceptor interfaces play a crucial role in the exciton-dissociation, charge-separation, and charge-recombination processes [1].

In this presentation, we discuss how the combination of state-of-the-art electronic-structure calculations and molecular dynamics simulations together with the results of temperature-dependent electroluminescence experiments: (i) allows a reliable description of the nature and energetic distribution of the CT electronic states; (ii) offers a unified description of the non-radiative voltage losses in both fullerene-based and nonfullerene-based devices; and (iii) provides clear guidance for the rational design of next-generation high-efficiency OSC blends [2].

[1] “Charge-Transfer Electronic States in Organic Solar Cells”, V. Coropceanu, X.K. Chen, T.H. Wang, Z.L. Zheng, and J.L. Brédas, Nature Reviews Materials, 4, 689-707 (2019).
[2] “A Unified Description of Non-Radiative Voltage Losses in Organic Solar Cells”, X.K. Chen et al., under revision (2020).