Nanoscale thickness and roughness control of gravure printed MEH-PPV layer by solvent printing for organic light emitting diode.

In this work, a nanoscale thick organic light emitting MEH-PPV (poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene]layer) was realized by gravure printing technology and its roughness was controlled by the solvent printing process. Also, an organic light emitting diode (OLED) was successfully fabricated by the gravure printing of MEH-PPV layers with surface treatments of solvent printing. There is strong demand for high throughput and large area processing technology for the commercialization of OLEDs and the gravure printing process is a good candidate. We applied gravure printing process technology to OLED fabrication in this work. We controlled the thickness of the organic layers by the multi-printing technique. To control the roughness of the MEH-PPV organic layer, solvent printing was proposed in this work with various solvent mixture of chloroform, chlorobenzene and 1,2-dichlorobenzene on the top of the gravure printed MEH-PPV layers and a significant reduction in roughness was achieved. We were able to achieve a 51 nm thick and 3.7 nm rough MEH-PPV layer with the gravure printing process and subsequent solvent printing treatment and an OLED was fabricated using the gravure printed organic layers. An improvement of the brightness and efficiency was observed due to the improved roughness of the organic layers.