Chen Wei-Ling, Chen Shan-Yu, Huang Dun-Cheng, Luo Dian, Chen Hsueh-Wen, Wang Chih-Yuan, Chang Chih-Hao
Department of Electrical Engineering, Yuan Ze University, Taoyuan 32003, Taiwan.
Institute of Lighting and Energy Photonics, National Yang Ming Chiao Tung University, Tainan 71150, Taiwan.
Materials (Basel). 2021 Sep 30;14(19):5723. doi: 10.3390/ma14195723.
Organic light-emitting diodes (OLEDs) used as phototherapy light sources require sufficient spectral distribution in the effective wavelength ranges and low operating voltages. Herein, a double emitting layer structure consisting of a red-emitting Ir(piq)acac and a deep-red Ir(fliq)acac was designed to generate a broad electroluminescence spectrum. An efficient TCTA:CN-T2T exciplex system was used as the host of the emitting layer, facilitating effective energy transfer from the exciplex host to the red and deep-red phosphors. The materials used in the exciplex host were also used as the carrier transport layers to eliminate the energy barriers and thus increase the current density. The hole injection layer structures were varied to examine the hole injection capabilities and the carrier balance. The resulting optimized phosphorescent OLEDs with a broad spectral profile exhibit a 90% coverage ratio in the target ranges from 630 to 690 nm, together with a high peak efficiency of 19.1% (10.2 cd/A and 13.8 lm/W). The proposed device only needs 5.2 V to achieve a power density of 5 mW/cm, implying that the device could be driven via two series-connected button cell batteries. These results illustrate the feasibility of our design concepts and demonstrate the realization of a portable and lightweight OLED phototherapy light source.
用作光疗光源的有机发光二极管（OLED）需要在有效波长范围内具有足够的光谱分布以及低工作电压。在此，设计了一种由红色发光的Ir(piq)acac和深红色的Ir(fliq)acac组成的双发射层结构，以产生宽的电致发光光谱。一个高效的TCTA:CN-T2T激基复合物体系被用作发射层的主体，促进从激基复合物主体到红色和深红色磷光体的有效能量转移。激基复合物主体中使用的材料也用作载流子传输层，以消除能量势垒，从而提高电流密度。改变空穴注入层结构以研究空穴注入能力和载流子平衡。由此得到的具有宽光谱分布的优化磷光OLED在630至690 nm的目标范围内显示出90%的覆盖率，同时具有19.1%的高峰值效率（10.2 cd/A和13.8 lm/W）。所提出的器件仅需5.2 V就能实现5 mW/cm的功率密度，这意味着该器件可以通过两个串联的纽扣电池驱动。这些结果说明了我们设计概念的可行性，并证明了实现一种便携式且轻便的OLED光疗光源。
