The Mobility Test System Building And Application Of Organic Semiconductor Materials

In recent years, organic semiconductor materials have developed rapidly and received concern attention, especially in the filed of solar cells, organic light emitting diodes and field effect transistor. To further improve the device structure and the efficiency of photoelectric conversion, the characteristics of the materials must be in depth study and research. As one of the important parameters of semiconductor materials, carrier mobility is able to reflect their characteristics. Accurate measurement of mobility, we can choose organic materials well, improve the molecular structure, make more perfect organic solar cell and research the electron or hole transport dynamics.It is difficult to measure for low mobility of organic semiconductor. So in this thesis, with the existing methods and our laboratory conditions, we decide to build a test system by the method of Time-of-FIight. Then we can achieve accurate measurement of organic materials mobility.The main works and conclusions are listed as following:1. We build the test system according to the method Time-of-Flight and then analysis the system parameters, such as laser wavelength, laser energy and sample resistor. In the experiment, NPB is a standard photoelectric material, deposited a film with 8μm. The results show that it is a little impact on transit time when laser energy and resistance are limited in a dozen micro-focus,1.5kΩFinally, in the air and room temperature, we get the hole mobility of NPB is 6.18×10-4cm2/Vs at a electric field 1.1×105V/cm. This result is in good agreement with the value witch is reported before. So our test system has good accuracy.2. With the test system, we measure the hole mobility of poly(3-hexylthiophene)(P3HT) which is widely used in photovoltaic devices. We drop-cast P3HT films 9.94μm from chloroform solution(10mg/ml) onto indium tin oxide(ITO) glass. The hole mobility is 3.8×10-4cm2/Vs at a electric field 5×104V/cm. In addition, we also measured the hole mobility of the polymer under various electric field. The results show that within electric field from 2×104V/cm to 1×105V/cm, the mobility has a negative electric field dependence. This is because the spatial disorder parameter exceeds the energetic disorder parameter.3. We also measured the hole mobility of four new kind organic compounds, their mobility is 7.8×10-4cm2/Vs,7.0×10-4cm2/Vs,5.6×10-4cm2/Vs and 3.4×10-4cm2/Vs at about electric field 105V/cm. Compared these value with NPB under the same conditions, the result show that the four compounds have good hole transport property, they can be used to improve device performance.