display luminescence from two channels: 1) relatively narrowband and vibronic unimolecular emission and 2) red shifted and always broadband and featureless PL from excimers or aggregates. This property encourages the use of Pt(II) complexes as single-emitter white light luminophores, for example, thanks to the mixing of luminescence from isolated and aggregated molecules. Aggregates of these complexes have recently been recognised as highly-efficient near infrared (NIR) emitters, achieving not only the best OLED external quantum efficiency (EQE) in this region of the spectrum, but also extremely long wavelength electroluminescence beyond 900 nm. Ongoing interest in the development of novel NIRemitting complexes requires easy-to-use tools for accurate prediction of their luminescence spectra and wavelengths. Although there exist qualitative empirical strategies to predict a red or blue shift in luminescence of said excimers or dimers, there exist no quantitative studies on predicting energy or spectrum of these excited state aggregates. For example, a recent study has shown a methodology for rapidly estimating PL spectra of monomeric luminophores, but there exists no similar study for excimeric platinum(II) complexes. The reported methodology requires only one computed parameter to draw the whole PL spectrum in which it supersedes other ways of predicting PL spectra. Popular density functional theory (DFT) and time-dependent DFT (TDDFT) methods are comprehensive to most material scientists and therefore are more likely to be used in real-life experimental work. Methods based on DFT are popular not only for their simplicity, but also accuracy in predicting certain properties of molecules. Mori and others have shown that TDDFT methods that include SOC with relativistic corrections can be used to accurately predicting phosphorescence lifetimes and zero-field splitting (ZFS) in metal complexes. Younker and Dobbs have demonstrated that a simple linear relation links the experimental and simulated excited state energy of organometallic complexes. The said correlation is different for S0 and T1 geometries.