Tetradentate Pt(II) Phosphors: A Computational Analysis of Nonradiative Decay Rates and Luminescence Efficiency

Cyclometalated tetradentate Pt­(II) complexes are a promising class of phosphors used in organic light-emitting diodes (OLEDs). We calculated decay rates and the resulting photoluminescence quantum yield (PLQY) for 17 recently reported tetradentate Pt­(II) complexes designed for OLED application. Several theoretical approaches for treating the 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 nuclear reorganization is required for the correct description of the relaxation process. Among different approaches for calculation of the nonradiative decay rate, the approximation constructed with the 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 the formulated method as suitable for practical application in the development of new Pt­(II) OLED phosphors.