Using ab initio approaches to model, predict and understand the optical properties of organic and inorganic dyes Denis Jacquemin Laboratoire CEISAM, UMR CNRS n°6230, Université de Nantes, 2, rue de la Houssinière, 44322 Nantes, Cedex 3, France. Denis.Jacquemin@univ -nantes.fr During this lecture, I will illustrate some of the successes and failures of Time-Dependent Density Functional Theory (TD -DFT) in simulating the properties of electronically excited -states, with a specific interest on structures of interest for dye chemistry. 1-2 Notably, I will discuss the importance of calculating vibronic effects to obtain accurate comparisons with experimental data, including 0 -0 energies and band shapes, and illustrate this aspect with several examples. 3 I will also present examples of applications of TD -DFT to real-life structures used in LEDs focussing on two examples: ESIPT -based organic dyes for white OLEDs 4 and inorganic complexes used in blue/green/red phosphors. 5 1 D. Jacquemin, C. Adamo, Chem. Soc. Rev., 2013, 42, 845 . 2 D. Jacquemin, C. Adamo, Top. Curr. Chem.. , 2016 , 368 , 345 . 3 F. Santoro, D. Jacquemin, Wires. Comput. Mol. Sci. 2016, 6, 460. 4 A. Steffen, K. Costuas, A. Bouccekkine, M. H. Thibault, A. Beeby, A. S. Batsanov, D. Jacquemin, A. Charaf -Eddin, J. F. Halet, T. D. Marder Inorg. Chem. , 2014 , 53 , 7055 . 5 E. Heyer, K. Benelhadj, S. Budzak, D. Jacquemin, J. Massue, G. Ulrich Chem. Eur. J ., 2017, 23, 7324 . 6 D W . Zhang, D. Jacquemin, Q. Peng, Z. Suhai, D. Escudero, J. Phys. Chem. C, 2018 , 122 , 6340 .