Oled Failure Analysis Technique

Due to their intriguing physical advantages such as low driving voltage, high luminescence, wide view angle, quick response and simple fabrication processes, organic light-emitting devices(OLED) is a novel technology for panel display with great prospect, and it will become the first choice of environment-friendly display technique. The main obstacles of extensive application of OLED are its low luminescence efficiency, short life time and low performance stability. Failure analysis of OLED, study the failure analysis, exploit new analysis methods, have a great meaning in enhancing the reliability of OLED.It's found that the problem of OLED packaging may cause shrink of light-emitting area of OLED. The rules of shrinking of light-emitting area under different circumstance such as air, dry air, wet Nitrogen were studied and the morphology of cathodes and organic layer of failed devices were studied by optical microscope and scanning electron microscope (SEM). The results showed that H₂O and O₂ would both affect the light-emitting area: H₂O would cause bubbles on cathode and crystallization of organic material, O₂ on the other hand, would cause oxidation of cathode and organic layer.The structure of OLED was studied by N&K analyzer, and the reflectance of samples kept in dry air for different time duration and the failed device were compared with each other. The structure information of OLED can be obtained by calculating and fitting experimental results. Through comparing the structure of different samples, we found out that for devices with structure of ITO/NPB/Alq₃/LiF/Al, the main causes of device failure are rooted in Alq₃ and LiF layer. N&K analyzer is an effective new method for failure analysis of OLED is also proved.Lead corrosion of organic light emitting diodes is an important cause of OLED device failure. X-ray diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS), scanning electron microscope (SEM) and energy dispersion X-ray (EDX) methods were conducted to analyze the product and the morphology of eroded Cr coated ITO lead sample, which is used in OLED. The results of XRD and XPS showed that Cr(OH)3 and CrO3 was obtained from corrosion reaction, and the results of SEM and EDX indicated that ITO was eroded afterward. Then, the polarization curves of lead samples in various solutions were analyzed, the results showed the valences of Cr in Chromium compounds were related to the potential of Cr and Cl(?) can accelerate corrosion reaction of ITO. At last, a simplified model was put forward to explain the whole process of lead corrosion according to the results above.