应用表面等离激元提高有机发光器件效率的研究进展

Progress of efficiency enhancement of organic light-emitting diodes via surface plasmon

表面等离激元(SPP)存在于金属和介质界面,是光场和金属表面自由电子相互作用而产生的电子集体振荡行为.一方面,由于在金属纳米颗粒表面会形成局域的SPP震荡(LSP),可以调控金属表面附近分子的发光性质,因此,很多研究者尝试在有机电致发光器件(OLED)中引入金属纳米颗粒,利用LSP改善OLED器件性能;另一方面,在传统发光器件中,由于金属表面等离激元的波矢量和自由光波的波矢量不匹配,无法辐射成自由光波,最终只能以热能的形式耗散掉.通过改变金属表面形貌,如附加光栅结构等方法,使得SPP的能量能够耦合成自由光,从而提高发光器件的外量子效率.利用SPP来提高有机发光器件的效率,已经引起广泛的关注,本文着重综述以下两个方面的工作:一是采用金属纳米颗粒的LSP提高荧光分子辐射跃迁的几率,从而提升发光器件的内量子效率;二是利用有序或无序光栅结构使得SPP与自由光的波矢匹配来提高器件的耦合出光,从而提升外量子效率.

The surface plasmon polariton （SPP）, exists at the interface of metal and media, where the optical field and the free electron can interact with each other and results in an oscillations of collective electrons. On one hand, a localized surface plasmon （LSP） can be formed on the surface of metal nanoparticles, and then the quantum yield of fluorescent molecules near the surface metal can be enhanced by the LSP. Therefore, many efforts have been paid to add metal nanoparticles into organic light-emitting diode （OLED） to improve its performance. On the other hand, in a conventional device, SPP can＇t emit light to free space because the wave vector of it doesn＇t match to that of free light, and then dissipates as heat. By changing the morphology of the metal surface, such as grating structure, the energy of SPP can be coupled into free light field, and the external quantum efficiency of device can be enhanced. It has been widely concerned on SPP to enhance the efficiency of OLED. This article reviews the progress on the following two aspects. Firstly, enhancing the rate of radiative transition of fluorescent molecules by using LSP of metal nanoparticles, which can enhance the internal quantum efficiency of organic light-emitting diodes; Secondly, emiting a light via matching the wave vector of SPP to that of free light with a grating structure of periodicity or unperiodicity, which can enhance the external quantum efficiency of OLED.