Photovoltaic (PV) technologies are gaining considerable interest as one set of the most promising technologies for clean and renewable solar energy conversion. And thin film PV technologies are highly attractive for low cost applications. Meanwhile, it is worth pointing out that efficient light absorption is crucial for high-efficiency thin film PV devices. As such, a variety of three-dimensional (3-D) nanostructures, such as nanowires, nanopillars, nanopyramids, nanocones, nanoholes, etc., have been extensively studied for improving the performance of thin film PV devices, utilizing various advanced light management schemes. However, in the past such kinds of nanostructures have been mostly fabricated with costly lithographic and etching processes which limit their practical applicatio...[ Read more ]

Photovoltaic (PV) technologies are gaining considerable interest as one set of the most promising technologies for clean and renewable solar energy conversion. And thin film PV technologies are highly attractive for low cost applications. Meanwhile, it is worth pointing out that efficient light absorption is crucial for high-efficiency thin film PV devices. As such, a variety of three-dimensional (3-D) nanostructures, such as nanowires, nanopillars, nanopyramids, nanocones, nanoholes, etc., have been extensively studied for improving the performance of thin film PV devices, utilizing various advanced light management schemes. However, in the past such kinds of nanostructures have been mostly fabricated with costly lithographic and etching processes which limit their practical applications.

In this thesis, a variety of controllable 3-D nanostructures, such as nanowells, nanopillars, nanocones, inverted nanocones, integrated nanostructures, etc., have been developed with a cost-effective and scalable approach. Firstly, it was discovered that a properly designed nanowell array can serve as an efficient photon harvester, and there exists a matching principle between the periodicity of the nanowell arrays and the wavelength for the optimal photon harvesting. In addition to naonwells, nanopillars and the integrated-nanopillar-nanowell structures were further obtained. It was demonstrated that the integrated nanostructures show more efficient light absorption than the nanowells or nanopillars over a broad range of wavelengths and incident angles. Additionally, amorphous silicon nanocones have been fabricated as nanophotonic structures with characterization of their intriguing optical anti-reflection property. Furthermore, low-cost, flexible and self-cleaning nanocone anti-reflection films have been achieved, which contributed to a conspicuous increase of device short circuit current density and power conversion efficiency. Moreover, thin film hydrogenated amorphous silicon solar cells have been fabricated based on various inverted nanocone substrates with omnidirectionally enhanced performance. These results demonstrate a viable and convenient route to fabricate high performance thin film PV devices for practical applications.