IMPROVED PERFORMANCE OF A FLUORESCENT BLUE ORGANIC LIGHT EMITTING DIODE WITH HOLE BLOCKING MATERIALS AS DOPANTS FOR TRANSPORT LAYERS

摘要

Realizing a highly efficient deep blue organic light emitting diode (OLED) with sufficient life time is the biggest challenge in the fabrication of full color OLED displays. Using hole blocking layers (HBL) has been an established technique to confine excitons or carriers in the recombination region. In the present work, we have doped the hole transport layer (HTL) and electron transport layer (ETL) with two different hole blocking materials and compared the performance of these devices with that of a standard device. Our standard blue OLED demonstrates a current efficiency of 2.3 cd/A. To improve its current efficiency, we have doped the ETL by a hole blocking material (Bphen), which shows no improvement in current efficiency. But, doping the HTL with another hole blocking material (TPBi) has led to current efficiency as high as 4.3 cd/A. The importance of band gap engineering is discussed based on the above studies.