Tetradentate Pt(II) Phosphors ？ a Computational Analysis of Nonradiative Decay Rates and Luminescent Efficiency

Abstract: Cyclometalated tetradentate Pt(II) complexes are promising class of phosphors used in organic light-emitting diodes (OLEDs). Prediction of the luminescent efficiency requires calculation of radiative and radiationless relaxation rates. We calculated decay rates and resulting photoluminescence quantum yield (PLQY) for 17 recently reported tetradentate Pt(II) complexes designed for OLED application. Several theoretical approaches for treating vibrational density of states in decay processes were utilized and systematically compared, using ab initio calculations as a source of input data. It was shown that along with the direct spin-orbit coupling and energy gap between initial and final states of transition, a proper account for the nuclear reorganization is required for correct description of the relaxation process. Among different approaches for calculation of the nonradiative decay rate, the approximation constructed with separate treatment of the slow and fast normal modes, was found to be the most accurate. The estimated error in prediction of the PLQY is about 10％, which allows to consider formulated method as suitable for practical application in development of new Pt(II) OLED phosphors.