Toward inkjet printing of small molecule organic light emitting diodes

Abstract

Thermal evaporation is the current standard for the manufacture of small molecule organic light emitting diodes (smOLEDs), but it requires vacuum process, complicated shadow masks and is inefficient in material utilization, resulting in high cost of ownership. As an alternative, wet solution deposition can provide significant cost savings by enabling high-volume, large-area electronics on flexible substrates at low fabrication costs. In this report we present inkjet printing as a method to produce three active layers in a smOLED stack: a hole-injection layer, a hole transport layer and an emissive layer. The OLED lighting application sets high demands to a uniform light output over an area. This requires homogeneous deposition of the electro-active layers and this poses a significant challenge. OLED device efficiency is greatly influenced by the printed layer morphology and the quality of the deposited layers. Therefore inkjet processed smOLED device efficiency will be compared with reference devices made via vacuum deposition.