15 June 2018

Solar-Tectic granted US patents for perovskite thin-film solar cells

© Semiconductor Today Magazine / Juno PublishiPicture: Disco’s DAL7440 KABRA laser saw.

Solar-Tectic LLC of Briarcliff Manor, NY, USA (which specializes in thin-film solutions for the solar, display, and glass industries) says that two patent applications for perovskite thin-film solar cells have been granted by the US Patent and Trademark Office (USPTO). The inventors are Solar-Tectic’s founding manager Ashok Chaudhari and the late Dr Praveen Chaudhari, renowned materials physicist.

The patents US 9,978,532 ‘Maximizing the Power Conversion Efficiency of a Tin Perovskite/Silicon Thin-Film Tandem Solar Cell’ and US ser. 15/157,539 ‘Methods of Growing Heteroepitaxial Single Crystal or Large Grained Semiconductor Films and Devices Thereon’ are part of Solar-Tectic’s ‘Tandem Series’ of solar cell technologies that includes a variety of different proven photovoltaic materials such as III–Vs, copper zinc tin selenide (CZTS) and amorphous silicon (a-Si) for the top layer on top of a silicon (or germanium) bottom layer, on various substrates such as cheap soda-lime glass. Tandem Series cells are claimed to have the potential to surpass the efficiencies of existing thin-film solar cell technologies such as cadmium telluride (CdTe), copper indium gallium dislenide (CIGS) and a-Si as well as incumbent silicon technology (based on poly- and monocrystalline wafers). 

Recently perovskite materials have gained much attention as a promising solution to the long-standing problem of solar cell efficiency. While there have been many reports of perovskite/silicon (wafer) tandem solar cells (and extensive intellectual property), there have been none on a perovskite/crystalline silicon thin-film tandem solar cell, until Solar-Tectic’s recent development (www.nscj.co.uk/JECM/PDF/3-2-2-Chaudhari.pdf).

Wafer-sized bottom poly- and monocrystalline silicon layers in PERC (passivated emitter and rear cell), PERL (passivated emitter with rear locally diffused), HIT (heterojunction with intrinsic thin-layer), HJ (heterojunction) or perovskite/silicon tandem cells are typically 200–280μm thick, whereas Solar-Tectic’s thin-film crystalline inorganic bottom layers can be as thin as 20–30μm with the same or similar efficiency. Moreover, they can be processed at much lower temperatures, lowering production costs significantly. The top perovskite layer is less than just 1μm (an ultra-thin film) and a thin-film crystalline silicon (CSiTF) bottom layer decouples the need for a silicon wafer. If the price of polysilicon rises less, silicon material use will be an additional cost saving.

Tandem perovskite solar cells are theoretically capable of 45% efficiency, although Solar-Tectic has set a more realistic 30% efficiency goal, higher than the 25–26.6% efficiencies for the best silicon wafer technologies such as PERC, PERL, HIT, HJ cells. The efficiencies of existing solar cells on the market in general are 14-25%. Solar-Tectic reckons that a cost-effective 30%-efficient solar cell with a simple design could revolutionize the solar energy industry by dramatically reducing the balance of system (BoS) costs.

Importantly, the entire Solar-Tectic process is environmentally friendly, since non-toxic tin (Sn) or gold (Au) is used to deposit the crystalline silicon thin-film material for the bottom layer in the tandem/heterojunction configuration as well as in the top perovskite layer. The more commonly used toxic materials lead (Pb) is not used in the perovskite.

Also, the manufacturing methods used – sputtering or electron-beam evaporation – are conventional and similar to those used in today’s thin-film solar cell industry as well as in the display industry (with which there is much overlap and potential for synergy).

A paper reporting a step in the ‘Tandem Series’ approach was recently published (www.sciencedirect.com/science/article/pii/S0167577X18302945). In March 2017, Solar-Tectic announced the first patent ever granted for this perovskite/silicon thin-film tandem approach.

A patent for a copper oxide thin-film tandem solar cell has also been granted to Solar-Tectic (US patent 9,997,661), expanding the IP portfolio of the Tandem Series.

R&D on the new perovskite thin-film tandem technology began last year at Maryland-based Blue Wave Semiconductors Inc (which provides thin-film deposition equipment as well as coating services).

See related items:

Solar-Tectic granted US patent for low-cost, high-efficiency III-V thin-film tandem solar cell on glass substrate

Solar-Tectic granted US patent for tin perovskite/c-Si thin-film tandem solar cell

Solar-Tectic granted US patent for perovskite/ crystalline germanium thin-film tandem solar cells

Solar-Tectic awarded patent for low-temperature thin-film deposition on low-cost substrates

Solar-Tectic awarded US patent for single-crystal thin-film solar cell technology

Tags: Thin-film PV

Visit: www.solartecticllc.com