Small reorganization energy acceptors enable low energy losses in non-fullerene organic solar cells

Minimizing energy loss is of critical importance in the pursuit of attaining high-performance organic solar cells. Interestingly, reorganization energy plays a crucial role in photoelectric conversion processes. However, the understanding of the relationship between reorganization energy and energy losses has rarely been studied. Here, two acceptors, Qx-1 and Qx-2, were developed. The reorganization energies of these two acceptors during photoelectric conversion processes are substantially smaller than the conventional Y6 acceptor, which is beneficial for improving the exciton lifetime and diffusion length, promoting charge transport, and reducing the energy loss originating from exciton dissociation and non-radiative recombination. So, a high efficiency of 18.2% with high open circuit voltage above 0.93 V in the PM6:Qx-2 blend, accompanies a significantly reduced energy loss of 0.48 eV. This work underlines the importance of the reorganization energy in achieving small energy losses and paves a way to obtain high-performance organic solar cells. Minimising energy loss is important for achieving high-performance organic solar cells. Here, the authors design and synthesise two acceptors with small reorganisation energies and reveal the relationship between reorganisation energy and energy losses.

Automated summary

This study reveals the relationship between reorganization energy and energy losses by designing and synthesizing two acceptors with smaller reorganization energies, providing direction for achieving high-performance organic solar cells.