Light extraction efficiency of a conventional organic light emitting diode (OLED) remains limited to approximately 20% as most of the emission is trapped in the waveguide and glass modes. An etchless simple method was developed to fabricate two-dimensional nanostructures on glass substrate directly by using ultraviolet (UV) curable polymer resin and UV nanoimprint lithography in order to improve output coupling efficiency of OLEDs. The enhancement of the light extraction was predicted by the three-dimensional finite difference time domain method. OLEDs integrated on nanoimprinted substrates enhanced electroluminance intensity by up to 50% compared to the conventional device.

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A technique in ultraviolet nanoimprint lithography ͑UV-NIL͒ for the creation of three-dimensional ͑3D͒ nanopatterns in a single step is proposed. The single-step fabrication of 3D or multilevel structures has a multitude of benefits. Inherent in this is the elimination of a need for alignment for multilevel fabrications as well as being a cost effective and simple process. For 3D UV-NIL, a trial in the fabrication of multilayered stamps has been conducted employing two-photon polymerization and diamondlike carbon ͑DLC͒ coating technique. The DLC coating layer enables the polymer patterns to be used effectively as a stamp without the need for an antiadhesion material. Additionally, O 2-plasma ashing has the potential for an epoch-making improvement of the precision of polymer patterns with a linewidth of 60 nm. Overall, several fine patterns are imprinted using the multilayered stamp onto a UV-curable resist via a single-step process without any identifiable damage.

This study was performed to investigate dynamic resist filling in ultraviolet nanoimprint lithography. The effects of surface condition on flow behavior during the filling process, including the contact angle and the aspect ratio of recessed features, are presented through numerical simulations. The optimized surface conditions for good imprinting results were determined through numerical experiments covering a range of test conditions. A decrease in the feature aspect ratio of up to 0.5 resulted in a contact angle twice the original value. Complete filling occurred when the contact angle of the vertical side wall was as low as that of the substrate.

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