Herein, PM6:L8-BO is used as the main host system (binary) while the fullerene molecules PC61BM and PCBC6 are introduced to form ternary OSCs. The results highlight the important role of fullerenes to enhance the performance of binary non-fullerene acceptor-based cells by suppressing trap-assisted recombination and optimizing the active layer morphology. Power conversion efficiencies (PCEs) of binary OSCs were increased from 17.28% to 18.10% and 18.38% for the PC61BM- and PCBC6-based ternary OSCs, respectively. Furthermore, the addition of the fullerene molecules in the active layer provided the devices with enhanced long-term photo and thermal stability. Molecular dynamics (MD) simulations, for the first time, reveal the significant role of fullerene molecules as morphology regulators in non-fullerene acceptor (NFA)-based systems. Mini-modules with active areas of 3.8 cm² were fabricated, achieving PCEs of 12.90%, 13.32%, and 13.70% for the binary and ternary cells using PC61BM-and PCBC6-based ternary cells, respectively.

In my opinion, it is an interesting manuscript reporting TOSCs of non-fullerene acceptors and fullerenes ones, it shows in-depth characterizations. I believe it deserves to be published in Materials Horizon journal. However, I will comment on some issues that Authors could clarify:

1. In the introduction section, authors could also state that, at the laboratory level, currently PCE value for OSCs is close to 21%: https://doi.org/10.1039/D5EE00101C ; https://doi.org/10.1038/S41563-025-02305-8

2. Previously, some TOSCs have been reported, based on NFA and FA, particularly based on PM6:L8-BO and PCBM, with excellent PV performance, up to 18 % of PCE (see for instance: https://www.nature.com/articles/s41467-024-51359-w (certified efficiency over 20%) and https://doi.org/10.1002/smll.202308216). This PV performance has been reached by controlling morphology and charge transport properties; in this sense, it is no totally clear to me the novelty of this current manuscript, authors should clarify it.

3. In the Introduction section, the phrase “However, the interfacial and morphological behavior of the photo-active layer constitutions under illumination and thermal stress remains poorly studied and understood.” need references of support. Likewise, stability results (long-term photo and thermal) in Results and Discussion section should be discussed/compared with previous similar literature.

4. In Table 1, Jsc from EQE could be added. Further, authors state that “As expected, the incorporation of the different fullerene derivatives increases the Voc of the ternary devices compared to their binary counterpart.”, however, according to Table 1, this affirmation it is no clear, Voc variation is just around 0.01 V.

My recommendation term: major revision

I have carefully reviewed this R1 version of the manuscript, my concerns were adequately addressed, I accept it for publication.