Suppressing the non-radiative energy loss in non-fullerene-based organic solar cells via solid additives of racemic and isotactic nitroxide radical polymonothiocarbonates

Abstract

The larger non-radiative energy loss (ΔV^non-rad_oc) of the non-fullerene-based organic solar cells (NFAs-OSCs) has been demonstrated to be the main barrier to further boosting the efficiency of NFAs-OSCs. In response, extensive studies have been implemented, focusing on the optimization of the photoactive layer morphology, molecular engineering of donors and acceptors, and the development of multi-component NFAs-OSCs etc., thereby achieving a series of devices with markedly enhanced performance. As an emerging strategy, the utilization of nitroxide radical-conjugated polymer additives is also worthy of attention due to their ability to simultaneously enhance the performance and stability of NFAs-OSCs. In this study, the racemic and isotactic nitroxide radical polymonothiocarbonates (PTC-NOs, with the specific names of Rac-PTC-NO, (R)-PTC-NO and (S)-PTC-NO) are employed as solid additives to mitigate the ΔV^non-rad_oc of the NFAs-OSCs. Upon the addition of 0.5 wt% of Rac-PTC-NO, (R)-PTC-NO and (S)-PTC-NO, the PCEs of the PM6:Y6-based NFAs-OSCs are respectively improved from 15.73% to 16.59%, 17.30% and 17.40%. Besides, the reasons behind the improvement in the performance of the NFAs-OSCs from the representative photovoltaic material pair of PM6:Y6, such as the increase of the exciton dissociation probability, suppression of charge carrier recombination and mitigation of the non-radiative energy loss of the devices upon the addition of the PTC-NOs additives, are supported by and discussed through a set of comparative investigations. This work not only broadens the scope but also provides new insights for designing and developing efficient nitroxide radical-based polymeric additives to mitigate the non-radiative energy loss, thus further boosting the performance of NFAs-OSCs.