Enhanced efficiency of organic light emitting devices (OLEDs) by control of laser imaging condition

Laser Induced Thermal Imaging (LITI) is a laser addressed thermal patterning technology with unique advantages such as excellent uniformity of transfer film thickness, capability of multilayer stack transfer, high resolution and scalability to large-size mother glass. However, the deterioration of the device performance during imaging process has been an obstacle to use it as a commercial technology. To investigate a possibility of thermal deformation of organic materials as a transfer layer and a receptor layer during imaging process, we executed a preliminary annealing test by using standard green devices at various temperatures. By comparison of these results with those obtained from LITI devices, we found that the main reason of device deterioration could be originated from the mobility change of the organic layers. Hence, we developed the dwell time control technology to suppress the thermal impact during LITI process and we finally obtained current efficiency which is quite equivalent to that obtained from the standard evaporation devices.