Organic Light-emitting Device Performance

Organic electroluminescence is light-emitting phenomenon arising from luminescent materials in which electricity is transformed into light when turned appropriate voltage on. Organic light-emitting devices(OLEDs) has such advantages as higher fluorescence efficiency, wider selection of emission colors and easer to fabricate large size films,lower drive voltage, wider visual angle,quick response and simple fabrication techniques,therefore it has aroused more and more focus in color flat panel display and large area lighting application.However, there is a certain distance between the present organic light-emitting devices and the practical application,and a number of technical problems,such as the improvement of the brightness uniformity,the lifetime and the improvement of the color purity,has become the bottlenecks of OLEDs which constrained its development,so it needs urgent solutions.In this paper,the main jobs are mainly focused on the analysis of the scaling effect of OLEDs and the improvement of single-color devices' performances.In the first part of the paper,devices in different area of the ITO thin film as anode is prepared,and through the test and analysis of the optical and electronic performances,it is found that with the light-emitting area increasing,the device current density and brightness decrease,which can be attributed to the voltage drop of ITO anode.In addition,it is first discovered that the devices' efficiency and light-emitting area have certain relationship, further,based the theory of edge effects,a model is proposed to analyze and research the scaling effect of OLEDs.In the second part of the paper,series of dye-doped OLEDs have fabricated,and through the test and analysis of the optical and electronic performances,it is found that the brightness and efficiency of the doped device are higher than the non-doped device,and with the increase of the doping concentration,the device brightness and current efficiency increase and then decrease,it is because that the inter-molecular energy transfer efficiency between the host and the guest is gradually increase with the increase of doping concentration,and when achieved the best doping concentration,the light-emitting layer occurs exciton quenching phenomenon,which leads to the drop of the brightness and efficiency.Finally,the optimization of devices' encapsulation conditions is summarized. These results are expected to give insight for lighting applications and improving the performances of devices.