Large-area deposition technology of high purity organic thin film by gas flow deposition

Abstract

A gas flow deposition (GFD) system was developed to manufacture large-area organic light-emitting diodes (OLEDs) aimed for displays and lighting applications. Organic materials were thermally evaporated with a flow of heated argon as a carrier gas that transports small molecules through a hearted pass line. The uniform organic vapor flux generated by mixing gas flow was carried to a cool glass substrate surface. The GFD system has some significant advantages: (1) high material utilization efficiency; (2) large area thickness uniformity; and (3) high purity organic thin film. A N,N'-di(1-naphthyl)-N,N'-diphenylbenzidine (α-NPD) thin film with a high purity of 99.97% was obtained using the GFD system. The film properties such as morphology, and electrical and optical characteristics were almost identical with those of the films made by conventional vacuum thermal evaporation (VTE). In addition, good doping concentration controllability was confirmed by the co-deposited film with a thermally activated delayed fluorescence (TADF) material.