Studies Of The Application In Organic Light-emitting Diodes By Impedance Spectroscopy

Compared to the traditional LCD, OLEDs occupied the market rapidly in recent years attributed to its advantages such as the low energy consumption, wide viewing angle, high contrast, etc. It is considered the most likely to inherit and replace the liquid crystal. The research for OLEDs nont only in its efficiency and emission color contrast ratio, but also need in-depth exploration and performance optimization. Impedance spectroscopy was widely used in various fields for its less interference, wide test frequency range, low-cost test, etc. This paper mainly study the semiconductor device’s internal electrical characteristics by Impedance spectroscopy.In this paper, F4-TCNQ is used as a hole buffer layer for preparing Organic light-emitting diodes and single-hole carrier device, it can be seen that the existence of F4-TCNQ hole buffer layer can increase the hole carrier injection efficiency and improve the performance of Organic light-emitting diodes. The impedance spectroscopy of the device can be well understood by simpley adopting the conventional RC equivation circuits. The result affirmed the F4-TCNQ hole modified layer taken a important effect in the modified hole injection barrier.To further investigate the use of impedance spectroscopy in analyzing internal electrical properties of the organic semiconductor device, we use strong molecular material F4-TCNQ dope in m-MTDATA fabricate single-carrier device. It can be seen that the current density of the device increases with the doping concentration increases. Then we find that the depicted Nyquist impedance curve is different for electrical doping and modified simple structure. Combined with basic knowledge of physics and equivalent fit data, we believe that the differernt in Nyquist impedance curve with electrical doping due to the existence of a depletion layer, however we also identified the optimization and upgrading in device performance by doping F4-TCNQ.We compared differences in performance between the devices modified by different materials, we found that with the increasing bias the conductivity of various materials modify the single-carrier device the gap is increasing by down slope curve, this result reflects Different materials reduce different injection barrier, which lead to more carriers injected in device in the same condition and a lower relaxation time, thereby affecting the change in the impedance value. It also found that different material layers have modified organic layer diffusion phenomenon occurs, and increases in proportion to the degree of diffusion and the hole injection capability. It also found that the modified material can diffusion the organic layer, and there is a relationship between the ability to increase the extent and the degree of diffusion.