Advanced organic vapor-jet printing and its application to organic electronic devices

Abstract

This dissertation describes the study of the advanced organic thin-film deposition technology to solve the present technical issues like the pattern-resolution limit or the scalability limit in conventional vacuum thermal evaporation (VTE) method. Although the inkjet printing is regarded as an alternative technology, the organic thin-film by solution processing often causes the degradation of device performance and reliability. On the other hand, organic vapor-jet printing (OVJP) method is capable of a direct, mask-free patterning of organic thin films yet still utilizes the same organic small molecules used in thermal evaporation, and thus is regarded as a promising alternative that combines the benefits of the proven VTE technology and those of the jet printing technologies. The first part of the dissertation describes the construction of an OVJP system that is essentially similar to the one reported previously in the literature, and explores how the OVJP system can be improved to further enhance its applicability in organic devices. In particular, addition of the pre-heating zone controlling the tem-perature of carrier gas is shown to be highly effective in achieving quality organic thin-films.. By combining the optimal carrier gas temperature and the surface treatment of gate dielectrics, a high performance top-contact pentacene TFTs are demonstrated which exhibit a mobility of 0.46 (±0.03) cm2V??1s??1 and an on??off ratio greater than 107. In addition, a laser-based alignment system is introduced so that the OVJP system is compatible with high density integration and multilayer pattern definition. With this, all-printed bottom-contact pentacene TFTs with a mobility of 0.19 cm2V??1s??1 and an on??off ratio greater than 106 are demonstrated in a combinatorial approach based on reverse offset printing (ROP) of Ag electrodes and OVJP of pentacene channel layers. The role of carrier gas in the thin-film formation and that of ROP-Ag electrodes in contact resis...