新型高效有机电致发光分子延迟荧光机制的理论研究

量子效率低是制约有机发光二极管广泛应用的重要因素之一。近年来，人们发现基于反系间窜越机制，给-受体型有机电致发光分子的内量子效率可以接近100%，从而引起广泛关注，但对反系间窜越机制的理解尚存在许多问题，相关理论研究也尚未广泛开展。本项目将从第一性原理出发研究给-受体型有机分子激发态的电子结构特点，计算激发态之间的自旋轨道耦合常数及其跃迁速率，通过建立和求解速率方程，分析给-受体型有机分子激发态动力学过程，揭示给-受体型有机分子的反系间窜越机制。同时，深入研究给-受体型有机分子结构与单重激发态和三重激发态之间的能隙、自旋轨道耦合常数的关系以及对单重激发态振子强度的影响，并在此基础上，设计同时具有高的发光强度和内量子效率的新型有机电致发光分子。本项目的研究将给出反系间窜越过程清晰的物理图像，为设计高效有机电致发光分子材料提供重要理论依据和参考。

Low quantum efficiency is one of the decisive factors that restrict the applications of organic light-emitting diodes. Recently, the internal quantum efficiency of certain Donor-Acceptor (D-A) molecular organic electroluminescence materials has reached 100% through the reverse intersystem crossing (RISC) mechanism, which attracts worldwide attention. However, the driving forces behind the RISC mechanism are still not very clear due to the lack of related theoretical investigations. In this project, the electronic structure of D-A electroluminescent molecules will be studied at the first-principles levels. The spin-orbit coupling between the singlet and triplet excited states will be calculated. Based on the calculated transition rates, the corresponding rate equations will be solved to analyze the excited state dynamics, aiming to reveal the RISC mechanism of the D-A molecules. The relationship between the molecular structure and the energy gap as well as the spin-orbit coupling of the singlet and triplet excited states will be established. Their influences on the optical oscillator strength of the singlet state will also be examined. With these studies, the design strategy for new organic molecules with both high luminous intensity and high quantum efficiency will be offered. This project will present a clear physical picture for the RISC processes, and lay the foundation for the future design of new type molecular organic electroluminescence materials with high efficiency and brightness.