电场变化对有机磷光器件中激子形成影响的研究

激子形成区域随电场变化的移动会使得有机电致发光器件(OLEDs)的效率和色度发生改变，从而影响器件的性能。文章首先制备了两种OLED器件，器件1为ITO/PEDOT∶PSS/PVK∶Ir(ppy)₃∶DCJTB (100∶2∶1 wt)/BCP(10 nm)/Alq₃(15 nm)/Al，器件2为ITO/PEDOT∶PSS/PVK∶Ir(ppy)₃(100∶2 wt)/BCP(10 nm)/Alq₃(15 nm)/Al，研究了电场强度对单层多掺杂结构器件激子形成的影响。实验发现在多掺杂发光层中，随着电压的增加，Ir(ppy)₃,PVK和DCJTB的发光均增强，PVK和DCJTB发光增强更快。对其发光机制进行分析，认为较高电场下，载流子获得较高能量，更容易形成高能量激子，产生宽禁带材料PVK的发光;另一方面，从能级结构分析DCJTB的带隙较窄, 俘获更多的载流子发光更强。同时，在器件的电致发光(EL)光谱发现在460 nm处一新的发射峰, 发光随着电压的增大相对减弱。为了研究460 nm发光的来源，制备了器件：ITO/PEDOT∶PSS/PVK∶BCP∶Ir(ppy)₃(x∶y∶2 wt)/Alq₃(15 nm)/Al, 改变x, y的比值研究发现，460 nm处的发光依然存在，推测此发光峰应与PVK及BCP之间有关。

Study of Exciton Generation Region of Phosphorescent Light Emitting Devices Based on the Changing Electric Field

The changes of exciton generation region are influenced by varying electric field, which affect the color and efficiency performance of devices. Firstly, The authors fabricated two types of phosphorescent light emitting devices, device 1： ITO/PEDOT∶PSS/PVK∶Ir(ppy)3∶DCJTB (100∶2∶1 wt)/ BCP(10 nm)/Alq3(15 nm)/Al, and device 2： ITO/PEDOT∶PSS/PVK∶Ir(ppy)3 (100∶2 wt)/BCP (10 nm)/Alq3 (15 nm)/Al. The authors investigated the influences of electric field on exciton generation region in single-layer and multi-doped structure devices. Analysis of the electroluminescence spectrum under different voltages indicates that the emitting of Ir(ppy)3, PVK and DCJTB was enhanced with the increase in applied voltages. Compared to Ir(ppy)3, the emitting of PVK and DCJTB was prominently enhanced. This is because under high electric field it is easier for high energy carrier to generate high energy exciton, and the emitting of wide-band-gap material PVK is stronger; on the other hand, the authors investigated the results from the aspect of energy band gap. DCJTB is narrow-band-gap material, which can capture carrier comparatively easily and emit stronger light. At the same time, we obtained a new emission peak located at 460 nm, which becomes comparatively weak with increasing voltage. In order to explore the reason, we fabricated the device: ITO/PEDOT∶PSS/PVK∶BCP∶Ir(ppy)3 (x∶y∶2 wt)/Alq3 (15 nm)/Al. The 460 nm emission peak doesn’t disappear by changing the mass ratio of x and y. The authors speculate that the emission peak relates to PVK and BCP.