Enabling Low Nonradiative Recombination Losses in Organic Solar Cells by Efficient Exciton Dissociation

The achievement of high performance in organic solar cells (OSCs) is highly dependent on efficient exciton dissociation. However, a comprehensive understanding of the exciton dissociation process under photoexcitation in OSCs remains elusive. Herein, a prototypical system of PM6:Y6 is adopted to explore the exciton dissociation process. An organic semiconductor PCz with distinctive photoexcitation signals from PM6 and Y6 is incorporated as the third component. Femtosecond transient absorption spectroscopy demonstrates clear cascade charge transfer processes in ternary PM6:PCz:Y6 system. These cascade channels contribute to enhancing the efficiency of exciton dissociation. Consequently, the nonradiative recombination energy loss is reduced, resulting in an improved power conversion efficiency (PCE) of OSCs. Furthermore, the reduction of energy loss is verified in different OSCs. When PCz is introduced into the D18:L8-BO system, a low nonradiative recombination energy loss of 0.175 eV is demonstrated, contributing a PCE of over 19%. This work highlights that the insight of efficient exciton dissociation enables low nonradiative recombination losses for efficient OSCs. A wide-bandgap organic semiconductor PCz as the third component in PM6:Y6 system reveals efficient exciton dissociation feature in ternary organic solar cells. Nonradiative recombination losses are reduced, resulting in an improved power conversion efficiency in organic solar cells. image