Preparation And Properties Of Gas Sensor Based On Oled Research

With the rapid development of modern science and technology, gas sensors are applied more and more widely in the fields such as mine exploration, semiconductor industry and health care. At the same time, the organic electroluminescent devices (OLED) as the new-generation display devices, which have the advantages of self-luminous, high brightness, low power and so on, are considered as one of the most promising flat panel display devices. The core of the thesis is to integrate these two technologies and prepare new type gas sensors based on organic electroluminescent devices.1. Vacuum evaporation method was adopted to prepare the devices with two different structures. ZnPc was used as the sensitive material in the first struture of ITO/NPB (30nm)/Alq3(50nm)/ZnPc (3nm/5nm)/Mg:Ag (10:1,200nm); Red fluorescent material DCJTB and red phosphorescent material Ir(piq)3were used as sensitive material in the second structure which was composed of two parts:the blue OLED excitation source and the sensitive film. Besides, a testing platform was built to test and analyze the prepared devices. The current-voltage curve and brightness-voltage curve measured in the air environment showed that the prepared devices had a typical rectifying characteristic of semiconductor diodes.2. In the N2environment, the current of ZnPc sensor would gradually decrease, but the brightness would gradually increase and finally remained unchanged. The changes of parameters for properties in NO2and NH3environment were tested and analyzed. The results showed that the oxidative gas NO2would reduce the devices’current and increase the brightness. On the contrary, the reducing gas NH3was able to improve the devices’current and reduce the brightness. The more the gas concentration increased, the more the devices’ properties parameters changed. The recovery of the devices was not so good and the repeatability was poor both in NO2and NH3environment. The response characteristics of devices with two different thicknesses were compared. The result showed that thinner devices had better sensing properties. At last, the sensitive mechanism of ZnPc sensos based on OLED was analyzed.3. Red fluorescent DCJTB and red phosphorescent Ir(piq)3were used as the sensitive material of the oxygen sensors. There was no change in sensors’brightness in N2environgment, which meant the devices had no sensitive effect in N2. The oxygen sensors had a certain degree of response to O2, and with the concentration increasing, the response increased too. Compared to the response of red fluorescent DCJTB devices, the response of red phosphorescent Ir(piq)3was more obvious. The devices with two kinds of sensitive films both had a certain degree of recovery and poor repeatability. Comparing the brightness response under different thicknesses of sensitive films, it’s found that the thinner one had a higher sensitivity and response speed. Finally, the sensitive mechanism of oxygen sensos based on OLED was discussed and analyzed simply.4. Overall, both the two structures had good gas selectivity, but the second structure had a faster response and a more disciplined recovery.