Investigation of Large-Area High Efficient Solar Cells by Birefringent Liquid Crystal Coatings

Due to the rising petroleum price and environment awareness, solar cells have become the best candidates for green energy resources, and the related industry has been quickly developed. However, the current status in product technologies and costs still require more research and development to provide sustainable growth, especially new material concept and novel device technology. The dominant silicon solar cell technology asks for suitable spectrum response, shallow contact, low surface recombination, antireflection, and surface rough structures, etc. Because silicon has high refractive index, the reflection is as high as 30~40%. This problem can be partially overcome by anti-reflective multilayer of suitable refractive index. The other prevailing technology has been anisotropic chemical etching of (100) silicon wafer, and nano and micro pyramids of (111) planes can be produced. The roughened pyramid structure invites extra light deflection, reduces reflection, and increases photon path, thus improves light absorption in the active layers of solar cells. In this project, we designed and prepared novel liquid crystal coatings for large-area solar cells. The optical birefringence characteristics could reduce the light reflectance, both low and high incident angles, from silicon substrates and anisotropically etched pyramid structures. The anti-reflection coatings would improve light absorption and solar cells’ total opto-electric conversion efficiencies. Thus, we designed novel anti-reflection coatings based on liquid crystal materials, and analyzed microstructures and anisotropic optical characteristics. The large-area reflectivity was significantly reduced. In addition, to investigate silicon solar cells with the novel liquid crystal coatings and several types of etched silicones, including I-V curves and opto-electric conversion efficiencies. Also, to prepare and synthesize vertical alignment liquid crystal precursor solutions, studying chemical formulation, viscosity, spin-coating parameters, and UV curing conditions. To further study higher incident angle effects on optical characteristics and interfaces and to evaluate the liquid crystal coatings for other thin-film solar cell systems.

Project ID:PB10308-2712
External Project ID:MOST103-2221-E182-058