Understanding the Mechanisms of White Light Emission of a Tetradentate Pt Complex in Various Surrounding Environments

For the great progress in panel display devices, it is necessary to have a thorough understanding of white organic light-emitting diodes (WOLEDs). In this work, we confirmed a reasonable mechanism of the white light emission with dual emission peaks in the studied compound; the mechanism is that the white emission could be formed with the 0–0 peak and the low-energy emission peak, where the latter is constituted by the high-frequency normal modes with larger Huang–Rhys factors. Moreover, in order to systematically understand the work performance in different surrounding environments, the emission spectra in solution, crystal phase, and amorphous phase were simulated. In view of the fact that the maximum emission wavelength of this complex corresponds to the 0–0 peak, the red-shifted emission from the solution to the crystal phase in experiment could be attributed to the smaller energy gap of the d−π* transition and the lower reorganization energy of the ground state (λgs) in the crystal phase. Additionally, our calculations indicate that the smaller energy gap of the π–π* transition and the smaller λgsin the amorphous phase would cause the red-shifted emission from the crystal phase to the amorphous phase, where the smaller energy gap plays the primary role. In the meantime, it is found that vibronic couplings play a predominant role in photoluminescence efficiency changes caused by environmental effects. Our computational study will provide valuable information to the rational design of optical applications with white emission, which is meaningful to the future development of WOLEDs.