Fig. 1. Fabrication process of the periodic corrugations based on NIL. (a) Si template with 290 nm periodic corrugations. (b) PDMS was spin-coated on Si template. (c) Solidified PDMS film was peeled off. (d) The corrugations were transferred to PDMS template. (e) SU-8 was spin-coated on a pre-cleaned glass substrate. (f) Prepared PDMS template was placed on the SU-8 film. (g) NIL processes were applied. (h) The periodic corrugations were prepared on the substrate.

Fig. 2. The AFM images of corrugations (a) prepared on glass substrate by NIL and (b) after deposition of ultrathin Au electrode. (c) and (d) are the height profiles of corrugations on the substrate and Au electrode, respectively. The periodic corrugations before and after deposition of Au film show consistent surface morphologies.

Fig. 3. (a) Measured and (b) simulated absorption spectra of OLEDs based on Ag, Al, Au, Cu metal cathodes

Fig. 4. (a) The normalized absorption spectra of OLEDs based on Ag cathode (black line), Al cathode (green line), Ag_0.952Al_0.048 alloy cathode (red line), Ag_0.909Al_0.091 alloy cathode (blue line), and Ag_0.870Al_0.130 alloy cathode (magenta line), respectively. (b) The angle-dependent absorption spectra of OLEDs based on Ag_0.909Al_0.091 alloy cathode. The inset in (a) shows the absorption spectra of OLEDs based on various cathodes without normalization.

Fig. 5. EL performance of OLEDs based on Ag-Al alloy cathodes with and without corrugations. (a) Current density-voltage and (b) efficiency-current density-luminance features, and (c) normalized EL spectra of corrugated and planar OLEDs. (d) The angle-dependent EL spectra of the corrugated OLEDs under TM polarization. The inset in (a) shows the photos of corrugated OLEDs and planar OLEDs operated at 6 V.