Experimental Study Of Carrier Transport Process In Weak Photoconductive Material With The TOF Technique

Organic electrolumimescent devices have attrattracted increasing attention in recent years because it's production will create a huge market as a new technology. Nowadays researchers in this field throw themselves into exploring high electroluminescence efficiency,improving device architencture and otherwise.In contrast to the rapid progresses made in the experimental front,systematic and comprehensive understanding of the various processes and the measurement of the charge carrier mobility of organic electroluminescent material is very important.So the main content of the thesis is based on the course, in which a testing system of measurement of the charge carrier mobility of organic electroluminescent material was set up. In this courae, I have explored appropriate measuring parameters and achieved good testing effect.The content includes choosing method,detemining the parameters of instruments,constructing the system,preparing sample and measuring the carrier mobility finally.The main method in effect to measure the charge carrier mobility of organic semiconductor material is time of flight(TOF) technique.TOF technique is to measure the transit time directly.If the measrued transit time is T_tr,then one can deriveμ= L²/T_tr·V It is obvious that the precision of Ttr is the guarantee of the calculation of the mobility.But in ordor to apply Scher-Montroll's power relation,one requires that the quantity of charge produced by the laser pulse is much less than the product of the sample capacitance and battery voltage,so that the drifting charges perturb the external electric field as less as possible.Another requierment is that the circuit reaction timeÏ„=RC be much smaller than the transit time tT so that the measured photocurrent is the same as the drifting current in the sample.However,in many low mobility organic and polymeric materials,these conditions are sometimes difficult to be satisfied simultaneously.During the course of testing the photocurrent ofα-Se,Alq3 by the system,We found the result will appear irresponsible if these conditions are not satisfied well. In addition, The effects of excitation light wavelength, pulse width and choice of detector, et al. on the carrier mobility are discussed.At last we...