The patent, Ser. No. 15/266,720 titled “Amorphous silicon/crystalline silicon thin film tandem solar cell” is part of a “Tandem Series” of high efficiency and cost effective solar cell technologies by Solar-Tectic LLC with the potential to surpass the efficiencies of current thin-film solar cell technologies such as CdTe, CIGS, and a-Si, as well as the silicon technology which dominates the global market today based on poly and monocrystalline wafers.
Wafer sized bottom poly- and monocrystalline silicon layers in PERC, PERL, HIT, HJ cells are typically 200-280 microns thick, whereas ST's thin-film crystalline silicon (“CSiTF”) bottom layers can be as thin as 20-30 microns, or even less, and with comparable efficiency and without “kerf-loss”; moreover, they can be processed at much lower temperatures thereby further lowering costs of production significantly. The top amorphous silicon layer in the tandem configuration is less than only 1 micron – an ultra-thin film. The CSiTF bottom layer is not microcrystalline or nanocrystalline as is the case with other commercially available tandem or heterojunction solar panels on the market today. Rather, it is highly crystalline, oriented, c-axis aligned, and has large crystals or grains, which is why higher efficiency is possible.
Tandem silicon solar cells are capable in theory of 45% efficiency, though ST has set a more realistic 30% efficiency goal for now, much higher than the best silicon wafer technologies such as PERC, PERL, HIT, HJ cells. The efficiencies of today's solar cells on the market in general range from 14% – 25% and are almost always lower than reported lab efficiencies. A cost effective 30% efficient solar cell on the market with a simple design would revolutionize the solar energy industry by dramatically reducing the balance of system (BoS) costs and the number of solar panels needed. Fewer solar panels means lower costs. The silicon wafer technology based on polycrystalline or monocrystalline silicon, which is 90% of today's market, would become obsolete.
The patent covers semiconductor devices in general, and the technology can be used for the backplane of thin-film transistors (TFTs) which today are usually made of thin-film silicon (both amorphous and polycrystalline). TFTS are essential to LCD and OLED production.
It is important to emphasize that the manufacturing process used in this breakthrough technology is remarkably simple due to the uncomplicated design. Only processing techniques commonly found in today's solar and display industries are needed, such as sputtering and PECVD.
Recently, a paper reporting successful fabrication of the bottom layer for solar cells and TFTs was published: https://www.sciencedirect.com/science/article/pii/S0167577X18302945
