PBD的掺杂对PVK：Ir(ppy)3体系发光特性的影响

Effects of PBD on the Luminescence Properties of PVK:Ir(ppy)_3

从三线态激子的发光机理入手,研究了PBD作为电子传输材料对PVK:Ir(ppy)3体系的影响。实验中制备了单层器件ITO/PVK:Ir(ppy)3/PBD/Al,ITO/PVK:Ir(ppy)3:PBD/Al和双层器件,ITO/PVK:Ir(ppy)3:PBD/BCP/Al,其中PVK:Ir(ppy)3的掺杂浓度比例不变,通过改变PBD的掺杂浓度,其变化范围是PBD与PVK的质量比从0:100到20:100,制得了一系列器件,研究了它们的光致发光(PL)光谱和电致发光(EL)光谱。发现PBD这种电子传输材料的加入对器件的亮度有很大提高,当PBD与PVK质量比为10%时,器件亮度最大。

The effects of PBD on the luminescence properties of PVK ：Ir（ppy）3 codoped with PBD with lower concentration were investigated. Two kinds of devices with the structures of ITO/PVK ： Ir（ppy）JPBD/Al and ITO/PVK ： Ir（ppy）3 ： PBD/ Al were fabricated. PVK emission appears in the electroluminescence （EL） spectra of ITO/PVK ： Ir（ppy）3/PBD/Al. The reason is that the Forster energy transfer is not efficient enough in the emission layer, and then the emission layer was doped with PBD. A set of devices were fabricated with the configuration of ITO/PVK ： Ir（ppy）3 ： PBD/BCP/Al. The doping weight ratio of PVK ： Ir（ppy）3 was fixed as 100 ： 1, and the weight ratio of PBD changed from 100 ： 0 （PVK ： PBD） to 100 ： 20. The photol （PL） spectra and electroluminescence （EL） spectra of these devices were measured. Through the analysis of their luminescence, it was found that the brightness of these devices codoped with PBD is improved. The brightness of these devices increases with increasing PBD doping ratio as the ratio does not exceed 100：10（PVK ： PBD）. The PBD codoping enhances the injection and transportation of electron, resulting in the enhanced carrier recombination probability. If the doping ratio of PBD exceeds 100 ： 10（PVK ： PBD）, the brightness of the device decreases. There are two reasons. One is that the superfluous PBD causes the carriers to be imbalanced and induces a larger leakage current. The other is that the superfluous PBD may block the hoping of holes or electrons between the PVK chains. The brightness is the strongest when the weight ratio of PVK to PBD is 100 ： 10.