Research On Luminescence Properties Of OLED Devices Based On Micro-nano Material And Structure

With several decades of research and development, organic electroluminescent technology has made a great breakthrough in lighting theory, functional materials and devices’ performance. But the luminous efficiency is still not high enough. The internal quantum efficiency of fluorescent device is not more than 25%, and the external quantum efficiency of phosphorescent devices is only about 20%, although its internal quantum efficiency can reach 100% in theory. Therefore this paper bases on basic structure devices, through optimizing devices’ electronic transport layer to improve the internal quantum efficiency of devices. Then from the perspective of the output efficiency of OLED devices, we prepare micro lens array in the outside of devices’ lighting surfaceto to enhance the external quantum efficiency. The specific work is as follows:First of all, we research on the different electronic injection materials, electronic transport material of Bphen and doping layer of Bphen:Cs₂CO₃ allow of the aspect of optimizing electronic transport layer. Results show that CS2CO3 has higher electronic injection ability than LiF in modifying cathode. Bphen, as electronic transport layer, can enhance electronic transport and injection ability, increase luminance and efficiency, and extend devices’lifetime. However, it will increase the turn-on voltage at the same time. When Bphen is 25nm, the turn-on voltage, maximum luminance and current effiency, lifetime are 2.65V,26500cd/m2,7.0cd/A and 364.5h respectively.Bphen:Cs₂CO₃ aselectronic transport layer can improve devices’ performance comprehensively. When the doping volume ratio of CS2CO3 is 15%, the turn-on voltage, maximum luminance and current effiency, lifetime are 2.45V, 28100cd/m2,4.2cd/A and 121.8h respectively.Secondly, we simulate the influence of parameters of micro lens array on output effiency by use of optical software of Tracepro. The smaller the interval, the higher the output efficiency. The larger the contact angle, the higher the output efficiency, when the contact angle of micro lens array is 90°, the output efficiency is the largest. When the interval is constant, the output efficiency will increase at first, and then reduce with the diameter of micro lens increasing. Within a certain duty-ratio and under the same diameter and interval, the devices with alveolate micro lens array have a larger output effiency than those with orthogonal micro lens array.In the end, we make micro lens array in different sizes and apply these in green OLED devices. Compared to referential devices, micro lens array in large size increases output effiency by 52%, but the devices’optical haze is quite big. While micro lens array in small size increases output effiency by 40% and the devices’ optical haze is smaller. Besides, micro lens array doesn’t influence the luminescence peak position.