Although both the logarithmic and radical functions can describe the correlation, the radical function slightly better (R = 0.83) than the logarithmic (R 2 = 0.74), both show that a small HOMO-LUMO gap calculated with GFN2-xTB would correlate with a small HOMO-LUMO gap calculated using DFT. As GFN2-xTB is a semi-empirical method, it is much faster than DFT and can greatly accelerate the GA. We therefore use GFN2-xTBcalculated HOMO-LUMO gap in the GA, and find oligomers that minimize the HOMO-LUMO gap with every generation.