Undercut structures fabricated by microtransfer printing combined with UV exposure and their applications

In this paper, the undercut structures were fabricated by microtransfer printing of metal films on the surface of photoresist combined with UV exposure and photoresist film developing. The patterned metal films were used as mask to realize the selective UV exposure of photoresist firstly. The undercut structures, which consist of the top metal films and the patterned bottom photoresist, formed in the subsequent developing process because of the lateral dissolving of photoresist at the edge of the unexposed regions. The method proposed in this paper has wider tolerance to the changing of the patterning parameters, but without effect on the patterning resolution since the metal film was used as the top layer. The undercut structures were used as separators to pattern passive-matrix display of organic light-emitting diodes (OLEDs). No visible difference of the device performance was observed compared with the OLEDs patterned by the shadow mask.