Lastly, although xTB-ML is significantly faster than firstprinciples methods, it is still too slow to screen millions of molecules. As stated previously, with our setup xTB-ML can calculate excited states of approximately 1500 molecules per hour (parallelized over 4 computer nodes), for molecules with < 50 heavy atoms such as those in PCQC. Therefore it would take over 3 months to calculate all 3.5M molecules in PCQC. While a definite improvement over TD-DFT (over 3 years), this is still slow. Expanding to larger databases with bigger molecules would increase runtime even further. Therefore, as a final direction, an optimized workflow using active learning could be implemented, intentionally searching for molecules with certain desired properties.