为了提高以TADF材料作为主体、天蓝色荧光材料作为客体的混合薄膜的OLED器件光电性能, 我们调整了器件结构, 使主体材料发挥其优势。制备了基本结构为ITO/NPB(40 nm)/DMAC-DPS∶x%BUBD-1(40 nm)/Bphen(30 nm)/LiF(0.5 nm)/Al的OLED器件。研究了主-客体材料在不同掺杂浓度下的OLED器件的光电特性。为了提高主体材料的利用率, 在空穴传输层和发光层之间加入10 nm的DMAC-DPS作为间隔层; 然后, 在阳极和空穴传输层之间加入HAT-CN作为空穴注入层, 形成HAT-CN/NPB结构的PN结, 有效降低了器件的启亮电压(2.7 V)。测量了有无HAT-CN的单空穴器件的阻抗谱。结果表明, 在最佳掺杂比例(2%)下, 器件的外量子效率(EQE)达到4.92%, 接近荧光OLED的EQE理论极限值; 加入10 nm的DMAC-DPS作为间隔层, 使得器件的EQE达到5.37%; HAT-CN/NPB结构的PN结有效地降低了器件的启亮电压(2.7 V), 将OLED器件的EQE提高到5.76%; HAT-CN的加入提高了器件的空穴迁移率, 降低了单空穴器件的阻抗。TADF材料作为主体材料在提高OLED器件的光电性能方面具有很大的潜力。

In order to improve the optoelectronic properties of organic light emitting diodes (OLEDs) with a hybrid film as the light emitting layer, which included the thermally activated delayed fluorescent (TADF) as host matrix and the sky-blue fluorescent material guest, we adjusted the device structures properly to improve the utilization rate of the host material. The basic structure of OLED is ITO/NPB(40 nm)/DMAC-DPS∶x%BUBD-1(40 nm)/Bphen(30 nm)/LiF(0.5 nm)/Al. First, the optoelectronic properties of host-guest OLED devices was studied with different doping ratio. Then, the DMAC-DPS (10 nm) was evaporated between the hole transport layer and the emission layer, it improved the utilization rate of the host material. Moreover, an organic material HAT-CN was added as the hole injection layer between the anode and the hole transport layer with the method of vacuum evaporation. Finally, the hole-only devices with or without HAT-CN were fabricated for the impedance spectra. The results indicated that the external quantum efficiency (EQE) of 4.92% was acquired at the optimal doping ratio (2%), it approached the theoretical EQE limit of the fluorescent OLEDs. The DMAC-DPS (10 nm) between the hole transport layer and the emission layer improved the utilization rate of the host material, led to a higher EQE of 5.37%, and breaked the limit of 5% of the EQE of traditional fluorescent OLEDs. The HAT-CN/NPB heterojunction units effectively reduced the driving voltage of OLEDs (2.7 V), and the maximum EQE increased to 5.76% at the same time. Additionally, From the lgJ-lgV curves and the impedance spectrum analysis, the hole-only devices with HAT-CN improved the hole mobility and reduced the impedance of the devices. This study shows that TADF materials have great potential in enhancing the optoelectronic performance of OLEDs.