Solar-Tectic LLC (ST) announced that a patent application for a CIGS thin-film tandem solar cell has been allowed by the US Patent and Trademark Office (USPTO). The patent (Ser. No. 15/238,050), is the first ever for a CIGS layer on crystalline silicon thin-film (CSiTF), and covers all inorganic materials, including germanium, for the bottom layer. “CIGS” stands for Copper Indium Gallium Selenide (or Sulfide), and is a proven thin-film photovoltaic material used by several thin-film solar companies today. The inventor is Ashok
While CIGS has attracted significant investment in the last decade, it has suffered from inadequate efficiencies and manufacturing processes. Typical CIGS efficiencies are 13-14% in the market, and the record (lab) module efficiency so far is ~18%. In order to compete with silicon wafer technology, used in 90% of today’s market, efficiencies must be as high as silicon or greater, ideally between 20% – 25%; this is true even if high speed and large scale CIGS manufacturing is possible. Such high efficiency is achievable in a tandem, heterojunction, configuration, since CIGS (or CGS) can be tuned to have a bandgap as high as the ideal 1.8eV (in tandem with silicon). No current matching is necessary in this design.
ST is now the only company in the world with a patent for a CIGS tandem cell with crystalline thin-films in both layers. The amount of crystalline silicon used in the Solar-Tectic CIGS/silicon tandem technology is much less than in a silicon wafer because the crystalline silicon is a very thin film.
The fabrication processes needed for this technology are conventional and similar to those used in today’s thin-film solar cell and display industries. A product patent application (US 2017/0271622) for this technology was also filed and is pending in the USPTO.
Importantly, the entire process for the CIGS tandem technology is environmentally friendly since non-toxic metals are used to deposit the crystalline silicon thin-film material for the bottom layer as well as in the top, CIGS, layer. The commonly used toxic selenium (and cadmium (CdS) window layer) is not used in the ST CIGS tandem technology here. Instead, sulfur is used.
Solar-Tectic LLC specializes in high-quality inexpensive thin-film solutions for the solar, display, and glass industries.
The company’s technology is based on the work of the late Dr. Praveen Chaudhari, renowned materials physicist, and recipient of the U.S. National Medal of Technology.