<p>Rhodamine 6G (R6G) is a highly versatile dye that has been observed to exhibits a photoluminescence quantum yield (PLQY) of close to 100%, but dimerization in R6G results in a decrease of PLQY. Here we use density functional theory and Redfield based excited-state dynamics to examine the photoluminescence of cationic and neutral R6G. Solvent effects are included by explicit solvation in methanol during the calculations. Nonadiabatic couplings between electronic and nuclear degrees of freedom are used to parametrize the rates of population transfer while radiative relaxation rates are computed using Einstein coefficients for spontaneous emission. The PLQY is then determined from the nonradiative and radiative relaxation rates. Our work agrees that R6G exhibits a PLQY near 100%, primarily due to the poor nonradiative relaxation rate, and will provide a good basis for future examinations into the effects of dimerization on photoluminescence.</p> Graphical abstract <p></p>