Wafer-scale high anti-reflective nano/micro hybrid interface structures via aluminum grain dependent self-organization

Surface anti-reflection (AR) with micrometer or nanometer scaled surface texture has been studied extensively and showed excellent light extraction (or harvest) performance in corresponding opto-electronic devices. In this paper, a 2-inch anodized aluminum oxide (AAO) template with nano/micro hybrid structure was obtained directly through a simple lithography-free aluminum anodization process for the first time. This new nano/micro hybrid structure combines the advantages of sub-100 nm sub-wavelength structure (SWS) and micrometer scaled surface roughening. Aluminum grains were found to rearrange the distribution of the penetrated surface current during the anodization and eventually induced the micrometer scaled fluctuation underneath. The ultra-thin AAO replication scheme was introduced to fabricate and study the spectrum (300 nm to 800 nm) dependent AR performance of the nano/micro hybrid PDMS structure, which obtained an AR enhancement fraction of more than 42% higher than that of the nano-patterned one. Thin film and GaN based light-emitting diode (LED, 450 nm) models were built and studied. Compared to the flat LED, the AR enhancement of the nano/micro structured one can reach as high as more than 3 folds. These results suggest the nano/micro hybrid structure could be a good alternative for the applications of surface AR structure.