Predicting luminescence spectra. The methodology for calculating PL spectra is presented in the ESI, sections 1 and 2. For each prediction of the PL spectrum of a given bimolecular state, the complex in question is excluded from the training set, leaving the other 22 dimers within it. This treatment does not show significant differences with the model using all 23 dimers (Table .4). In addition, the correlation is validated by randomly removing four complexes from the training set used to obtain the correlation. One can note that the said four datapoints (test set) show a perfect agreement with the trendline (Fig. .23). The predicted spectrum is modelled as a Gaussian curve by inverting the methodology used in fitting (see ESI Section 2 for mathematical details). This way the key properties of the spectrum can be visualised, including the proportion of light in the visible (<700 nm) and NIR (>700 nm) regionsfundamental factor when designing luminescent materials for NIR OLEDs. Fig. shows representative examples of predicted PL spectra superimposed on experimental data, while other spectra are presented in the ESI (Fig. .2-21). In general, the model PL spectra well describe the experimental data in the main region of interest from the onset to peak.