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.<br/><br/>In this presentation, we discuss how the combination of state-of-the-art electronic-structure calculations, fully quantum-mechanical 3-state vibronic approaches, 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.

High efficiency organic solar cells: Impact of non-fullerene acceptors

ACS Fall 2021

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