Fig. The combined absorption spectra of all four materials in the best tandem cells from GAs 5, 6, and 7, with depictions of the acceptor molecules and donor polymers. The numbers of each material are their index within their reference database 10%. This high-PCE dataset was used to train the OPEP2 PCE prediction model, an ensemble of random forest and neural network models. This model was used as a fitness function in the GAs for discovering new NFAs and donors, with an RMSE of 1.6 ± 0.14.