Investigation of nozzle printing parameters for OLED emitting layers

Solution processing, especially printing of OLEDs is an issue of current research. Among various types of printing, nozzle printing does not require complicated experimental procedures, and therefore it is a good example of investigating actual printing process in a laboratory level. Mixed red and yellow light emitting layers required for the implementation of white OLEDs have been fabricated by nozzle printing and their thickness characteristics by varying the printing conditions, such as solvent composition, printing pressure, and Y-pitch values, have been investigated. After nozzle printing parameter optimization, an OLED device by nozzle printing has been finally fabricated with the following structure, [ITO / PEDOT:PSS / PVK:Ir(BT)₂(acac): Ir(piq)₂(acac) / TPBi / LiF / Al]. The device efficiency of the nozzle printing device (5.26 cd/A) was comparable to the spin-coating device (5.61 cd/A), and this implies the potential of the nozzle printing process as a good alternative to the spin-coating process in solution processing.