Properties of Organic Molecules for Use in OVPD

These latest results demonstrate that decoupling deposition and micropatterning can be performed on industrial scale leading to sophisticated full-color displays. 

Besides chemical synthesis, purity of the employed chemicals is essential for the organic device performance desired. Small-molecule materials, which are only poorly soluble, are usually purified by repeated train sublimation, which results in substantial losses of material and additional purification costs. These material requirements are almost identical for OVPD and VTE. Because of the different deposition processes, the thermal stress on the organic materials is different in OVPD and in VTE. OVPD operates under steady-state temperature conditions without ramping of the evaporation temperature during processing, as is typically applied in VTE. Depending on the vapor pressure of the organic materials used and the 

There are similarities but also many differences between the deposition technologies VTE and OVPD. On the basis of a detailed technical evaluation of both technologies OVPD, as the new deposition technique, must produce results comparable with those of VTE and, additionally, advantages, to attract industrial attention. Besides overall hardware equipment differences, for example source containers and showerhead, these two technologies differ also in the principle of deposition on the molecular level. The individual process characteristics of OVPD and conventional VTE, which will be discussed below, are listed in Table 9.1. 

Use of a carrier gas in OVPD enables deposition of the organic materials at a pressure of 10 3-10 torr (Table 9.1, no. 1) whereas the VTE system must be pumped down to high-vacuum conditions, which is a time-consuming and critical 

8 System downtime Low because of hot wall design High because of particle generation 

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