Etch-free selective area growth of well-aligned ZnO nanorod arrays by economical polymer mask for large-area solar cell applications

A facile and cost effective solution method was used for the large-scale selective area growth of well-aligned ZnO nanorod arrays (NRAs) on a pre-patterned ZnO/Si. Conventional photolithography is employed to develop negative and positive circular ZnO NRAs micro-patterns with the help of low cost and economical flexible photo (polymer) mask. Unlike complex photolithography procedures, our patterning process does not require wet or dry-etching processes, and thus prove to be a simple, fast and low cost technique. Field emission scanning electron microscopy analysis reveals that the selectively grown ZnO nanorods have an average diameter and length of ∼55±5 and ∼650±50 nm. The structural analysis of ZnO nanorods showed that the nanorods were single-crystalline and grown along the c-axis direction. The photoluminescence spectrum shows a strong ultra violet emission at 381 nm and a broad deep-level visible emission at 580 nm. Such large-sized ZnO patterned substrate will be effective in light trapping and localized surface trapping, which can lead to significant enhancement in light absorption of solar cells.