Before optimizing tandem OSCs, high-performing NFA/donor pairs must be discovered. Using a series of genetic algorithms, new NFA small molecules and donor polymers are designed and their PCE evaluated with the OPEP2 model. It is difficult to concurrently optimize both materials, thus the first step is the discovery of new NFAs. Three GAs were performed to explore several classes of NFAs (e.g. fused-ring backbone with and without π-conjugated units and a five-unit unfused-ring backbone). All three GA runs were quickly able to find high-PCE NFAs, with the best NFA belonging to the fused-ring backbone with πconjugated spacers (GA 2) with a predicted PCE of 20.8% (Fig. ). This agrees with the current literature that extended conjugation and a rigid backbone can improve charge generation and transport . All three GAs appeared to have converged on the top candidate after 30-40 generations. The GAs discovered many high-performing NFAs, with 49 pairs having a predicted PCE greater than 20% and 1,244 with a PCE greater than 18% (ESI Table ).