Device Parameters Determination by Numerical Model Fitting for Organic Light-Emitting Diodes (OLEDs) using Impedance Spectroscopy Measurement

摘要

We have developed a numerical fitting methodology which enables the determination of device parameters for OLEDs from impedance spectroscopy (IS) measurement, temperature dependence measurement and dark injection space charge limited current (DI-SCLC) measurements.In our method, carrier mobility is estimated from DI-SCLC, density of state (DOS) and interface state density are obtained from model fitting of real/imaginary part of capacitance measured by IS, barrier height of interface is estimated by modified Schottky model fitting of temperature dependence current-voltage (I-V) measurements. Using this approach we have determined barrier heights, DOS, interface state densities, carrier mobilities and Richardson factors for each interface and layer in OLED devices.. In case of the ITO/NPD interface, barrier height, DOS, interface state density and ent methods for extraction of device parameters such as carrier mobility, density of state (DOS), barrier height. In these methodologies impedance spectroscopy (IS) is a useful tool for evaluating relaxation, transport and injection in various organic devices. Usually IS measurements allow the determination of equivalent circuits, DOS and carrier mobility of the organic semiconductor layers. In order to determine the carrier injection behaviour, we propose a numerical model and model fitting method included interface state density (D_(it)) for IS measurement results of hole-only devices (HOD) and electron-only devices (EOD). Therefore, a recombination model is also proposed for the negative capacitance behaviour of OLEDs. Naito et. al. have also proposed a numerical model included DOS of organic semiconductor for OLEDs. We obtain DOS from Naito's model and D_(it) from our model. D_(it) is expected to be a key parameter of the device degradation mechanism.