CPT and imec demonstrate an 1250 PPI OLED patterned using a photolithography process

Taiwan-based Chunghwa Picture Tubes (CPT), in collaboration with European research institute imec (in the framework of the Holst Centre collaboration) have demonstrated an ultra-high resolution OLED display that was patterned using photolithography - without the need for an FMM (metal mask). A photolithography process offers a high aperture ratio, large substrate sizes and good yield control.

The prototype display that was demonstrated is a passive display with a 1400x1400 resolution (or 1250 PPI!) of side-by-side orange and green OLEDs. imec reports that preliminary lifetime investigation shows operation of each color after patterning for a few hundred hours at more than 50% of the original brightness.

The two companies say that the one of the main challenges when applying standard photolithography to OLEDs is the fragility of the organic materials for the photolithography chemicals. To solve this issue, CPT and imec have used an i-line, chemically amplified photoresist system in a process flow dedicated to OLED stacks.