Small molecular glycosylated nitroxide radical additives enable efficient suppression of the non-radiative energy loss of non-fullerene acceptors-based organic solar cells

Journal article, 2026

Nitroxide radical-conjugated polymer additives (nr-PAs) have been employed as newly emerged additives to mitigate the non-radiative energy loss (Enon−rad^loss), thus to boost the performance and stability of the non-fullerene acceptors-based organic solar cells (NFAs-OSCs). Herein, the small molecular nitroxide radical compounds (SM-TEMPO) of racemic 4-glycidyloxy-substituted 2,2,6,6-tetramethylpiperidine-1-oxyl (GTEMPO), the stereoisomers of (R)-GTEMPO and (S)-GTEMPO, are employed as the additives for NFAs-OSCs. Upon addition of 1.0 wt% (relative to the weight of polymer donor) of the SM-TEMPO radical additives, the power conversion efficiencies (PCEs) of the devices improved as follows: PM6:Y6: from 15.73% (pristine) to 16.46% (GTEMPO), 17.20% ((R)-GTEMPO), and 16.91% ((S)-GTEMPO). D18-Cl:L8-BO: from 17.53% (pristine) to 18.66% (GTEMPO), 19.42% ((R)-GTEMPO), and 19.38% ((S)-GTEMPO). On the contrary, the addition of the unglycidylated 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) radical additive always results in a slight decrease in the PCEs of the PM6:Y6-based NFAs-OSCs. Moreover, the reasons behind the performance enhancement, as well as the specific correlation between the improved performances of NFAs-OSCs and the difference in aggregation behaviours between the SM-TEMPO and TEMPO radical additives, are investigated and discussed through a set of physical investigations of representative PM6:Y6-based blends and devices. This work not only demonstrates that SM-TEMPO radical additives, which tend to aggregate in the active layer, can serve as effective additives to improve the performance and stability of the NFAs-OSCs as their nr-PAs counterparts, but also points towards simpler avenues for the development of the nitroxide radical-based additives to achieve high-performance NFAs-OSCs with enhanced stability.