| dc.description.abstract | In this study, we discuss performance of micron-sized OLEDs, and compared with the millimetre-sized OLEDs. We use two lithography processes to fabricate micron-sized OLEDs. (1) The active area of OLED is defined by photoresist, (2) and etching ITO electrode to micron size. From the results, it can be seen that the breakdown current density of millimetre-sized OLED is 1 A/cm2. However, the breakdown current density of micron-sized OLEDs can rise to more than ten times. Among the micron-sized OLEDs, the maximum breakdown current density of 25×25 μm2 device is 58.3 A/cm2. Among two lithography processes, the breakdown current density of etching pattern-device is higher than blocking pattern-device. More importantly, the External quantum efficiency of micron-sized OLEDs are the same with millimetre-sized OLEDs. It can be seen that the high current density in the micron-sized OLEDs still possesses effective recombination luminescence, while the lithography process does not affect the luminous efficiency.
In this paper, the photolithography process is applied to BSB-Cz / PVK OLEDs with high current density. From the results, it can be seen that the device with smaller active area has a higher breakdown current density. The breakdown current density of the smallest micron-sized OLED (20×2000 μm2) fabricated in this experiment can rise to 3 A/cm2, and the external quantum efficiency is still above 1%. Compared to the device of 10 mm2, the breakdown current density can increase nearly 15 times. Although we didn’t find spontaneous emission amplification at the highest current densities, we still have successfully demonstrated the use of miniaturization process to enhance the OLED current density and maintain high luminous efficiency. The results of this research will be helpful to the further development of electrically excited organic laser in the future.
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