Bi-Layer Gravure Printed Nanoscale Thick Organic Layers for Organic Light Emitting Diode

The gravure printed single layer structure and bi-layer structure of MEH-PPV/rubrene organic light emitting diodes (OLEDs) were investigated in this work. Typically, the formation of bi-layers in polymer light emitting diodes (PLEDs) is challenging. The brightness and efficiency polymer light emitting materials were enhanced by the gravure printed bi-layer structure in this work. The layer structure of the OLED devices was glass/ITO/PEDOT:PSS/active layer/LiF/Al. The active layers were made using two different processes-one was a gravure printed single organic layer made of a blended mixture of MEH-PPV and rubrene, and the other was a gravure printed bi-layer of MEH-PPV and rubrene. The gravure printed bi-layer devices exhibited a higher brightness and efficiency than the blended devices. The efficiency of the bi-layer MEH-PPV/rubrene structure was improved by a factor of 1.6 similar to 3.2, and the brightness was improved by a factor of 1.9 similar to 2.0 compared to the blended single layer structure. This work demonstrated that organic bi-layers could be formed using gravure printing technology and the bi-layer structure exhibited a higher efficiency than the blended single layer structure.