Computational Strategies for Predicting Excited‐State Energies in Eu ³⁺ Down‐Shifting Spectral Converters for Photovoltaic Devices

In this work, a computational protocol has been developed to predict the ligand‐based low‐lying excited‐state energies of Eu 3+ coordination compounds with antenna ligands. A computational strategy, based on density functional theory (DFT) and time‐dependent density functional theory (TD‐DFT), has been developed using compounds with reliable structural and spectroscopic experimental data as a reference set. This approach aims to predict both the geometry and energy of the lowest‐excited triplet state, critical factors influencing the efficiency of the antenna effect and energy transfer to the Eu 3+ ion. The model not only shows the ability to replicate available experimental data at a relatively low computational cost, but also accurately predicts triplet‐state energies for compounds that have not been included in the training set. This work is a first step toward the development of an affordable method for accurate predictions of the quantum yield of lanthanide‐based complexes to assess their potential application as down‐shifting spectral converters in solar cells.