两种磷光材料在聚合物掺杂体系中的发光特性研究

Study on Luminescence Characteristics of Polymer Doped with Two Different Phosphorescent Materials

磷光材料由于可以利用电致激发所形成的单重态和三重态激子,因而可以得到接近100%的内量子效率。文章对常温下基于磷光材料Ir(ppy)3及Ir(piq)3掺杂PVK薄膜为发光层的器件的光学和电学特性进行了研究。光致发光的结果显示相同掺杂质量比下由PVK到Ir(piq)3的能量传递比到Ir(ppy)3更加困难。通过研究两种掺杂体系不同质量比的电致发光特性,可以认为这两种磷光器件的发光主要来自于磷光客体分子直接俘获载流子发光而非主体的能量传递。Ir(piq)3掺杂体系对掺杂比例的依赖更为明显,从能级结构分析,认为是由于Ir(piq)3的更低的HOMO及高的LUMO能级,而比Ir(ppy)3具有更好的载流子俘获和传输特性。

With the development of organic light-emitting diodes, interests in the mechanisms of charge carrier photo generation, separation, transport and recombination continue to grow. Phosphorescent organic light-emitting diodes have gained considerable interest in the last 10 years because of high luminance efficiency. In the present paper, the authors investigated the optical and electrical characteristics of the devices based on Ir（ppy）3 and Ir（piq）3 doped PVK matrix emission layer at room temperature. The PL spectra show that the energy transfer from PVK to Ir（piq）3 is harder than that of PVK to Ir（ppy）3. The Luminescence characteristics of devices with different doping ratio show that it is not the energy transfer from matrix, but the recombination of injected carriers on phosphorescent molecules that is the main origin of EL emissions. From the viewpoint of energy level, the characteristics of carrier-trap and transport in Ir（piq）3 are better than in Ir（ppy）3 due to the high HOMO and low LUMO in Ir（piq）3