Park Sang-Geon, Lee Won Jae, Song Min Jong, Shin Johngeon, Kim Tae Wan
Division of Smart Electrical and Electronic, Silla University, 140 Baegyang-daero 700beon-gil, Sasang-gu, Busan 46958, Korea.
Electrical and Computer Engineering, Stony Brook University, 100 Nicolls Rd, Stony Brook, NY 11794, USA.
Materials (Basel). 2019 Mar 22;12(6):966. doi: 10.3390/ma12060966.
We examined the electro-optical characteristics of organic light emitting diodes according to the N,N'-diphenyl-N,N'-di(m-tolyl)-benzidine (TPD) thicknesses. The thicknesses of TPD were varied from 5 nm to 50 nm. The current density of the device with a TPD thickness of 5 nm was 8.94 times higher than that with a thickness of 50 nm at a driving voltage of 10 V. According to the conduction⁻current characteristics of conductors, the current densities improved with a decreasing TPD thickness. Different from the current density⁻voltage characteristics, the current efficiency⁻current density characteristics showed an improved efficiency with a 50 nm TPD thickness. The current efficiencies of a device with a 5 nm TPD thickness at a driving voltage of 10 V was 0.148 and at a 50 nm TPD thickness 0.993 cd/A, which was 6.7 times higher than the 5 nm TPD thickness. These results indicated that hole transport in Organic Light-Emitting Diode (OLED) devices were more efficient with thin 5 nm TPD than with thick 50 nm TPD, while electron transport was more efficient with thick 50 nm TPD, which caused conflicting results in the current efficiency-current density and current density-voltage characteristics according to TPD thicknesses.
我们根据N，N'-二苯基-N，N'-二（间甲苯基）-联苯胺（TPD）的厚度研究了有机发光二极管的电光特性。TPD的厚度在5纳米至50纳米之间变化。在10伏的驱动电压下，TPD厚度为5纳米的器件的电流密度比厚度为50纳米的器件高8.94倍。根据导体的传导电流特性，电流密度随着TPD厚度的减小而提高。与电流密度-电压特性不同，电流效率-电流密度特性表明，TPD厚度为50纳米时效率有所提高。在10伏驱动电压下，TPD厚度为5纳米的器件的电流效率为0.148，TPD厚度为50纳米时为0.993坎德拉每安培，比TPD厚度为5纳米时高6.7倍。这些结果表明，在有机发光二极管（OLED）器件中，5纳米厚的TPD的空穴传输比50纳米厚的更有效，而50纳米厚的TPD的电子传输更有效，这导致了根据TPD厚度在电流效率-电流密度和电流密度-电压特性方面出现相互矛盾的结果。
