Studies of mist deposition in the fabrication of blue organic light emitting diodes

In this work, the process of mist deposition is explored as a method used to deposit organic semiconductors for applications in organic light emitting diodes (OLEDs). The deposition kinetics of a specially formulated hole transport agent is studied. The results indicate that the mist-deposited organic film thickness varies linearly with precursor concentration, deposition time and substrate potential. Depending upon process parameters, a deposition rate in the range of 50 nm min−1 is readily achievable. Evolution of surface roughness revealed distinct stages in the film formation process. The growth of secondary layers was observed before the formation of a complete initial film layer. A working OLED with the hole transport layer deposited by mist deposition was demonstrated. The luminance of the device was measured to be a maximum of 3000 cd m−2 and the efficiency was 6.7 cd A−1.