Method of forming semiconductor film and photovoltaic device including the film

Abstract

A method of depositing a kesterite film which includes a compound of the formula: Cu2−xZn1+ySn(S1−zSez)4+q, wherein 0≦x≦1; 0≦y≦1; 0≦z≦1; −1≦q≦1. The method includes contacting hydrazine, a source of Cu, and a source of at least one of S and Se forming solution A; contacting hydrazine, a source of Sn, a source of at least one of S and Se, and a source of Zn forming dispersion B; mixing solution A and dispersion B under conditions sufficient to form a dispersion which includes Zn-containing solid particles; applying the dispersion onto a substrate to form a thin layer of the dispersion on the substrate; and annealing at a temperature, pressure, and length of time sufficient to form the kesterite film. An annealing composition and a photovoltaic device including the kesterite film formed by the above method are also provided.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]The present invention relates to a liquid-based method for deposition of inorganic films having Cu, Zn, Sn, and at least one of S and Se, and more particularly to a method of deposition of kesterite-type Cu—Zn—Sn—(Se,S) materials and improved photovoltaic devices based on these films.[0003]2. Description of Related Art[0004]Large-scale production of photovoltaic devices requires high-throughput technologies and abundant environmentally friendly materials. Thin-film chalcogenide-based solar cells provide a promising pathway to cost parity between photovoltaic and conventional energy sources.[0005]Currently, only Cu(In,Ga)(S,Se)2 and CdTe technologies have reached commercial production and offer over 10 percent power conversion efficiency. These technologies generally employ (i) indium and tellurium, which are relatively rare elements in the earth's crust, or (ii) cadmium, which is a highly toxic heavy metal.[0006]Copper-...

AI Technical Summary

Benefits of technology

[0045]Another advantage of the present invention is to avoid or reduce the necessity of enhancing additives, in particular organic polymers acting as binders, surfactants and / or extenders, as their function can be substantially engineered by adequate introduction of desirable dissolved components that are subsequently incorporated into the final composition.

[0046]Nevertheless, in cases where additive use is desirable or in cases where such additives can be conveniently eliminated, e.g., by thermal anneal in oxidizing atmosphere when oxide materials are targeted, these can be readily used. Therefore, in addition to the above 3 principle components the ink may optionally contain enhancing additives that improve the dispersion of the solid phase and / or the solubility of the liquid phase and / or the rheological properties of the ink.

[0047]Some non-limiting examples of such additives include: binders, viscosity modifiers, pH modifiers, dispersants, wetting agents and / or solubility enhancers, such as, polymers, surface active compounds, complex forming agents, e.g., amines, and acidic and basic substances.

[0048]The deposition of the prepared ink on a substrate can be accomplished by forming a liquid layer of the ink by any standard liquid-coating technique, such as, but not limited to, spin coating, dip coating, doctor blading, curtain coating, slide coating, spraying, slit casting, meniscus coating, screen printing, ink jet printing, pad printing, flexography, and gravure printing.

[0049]The substrate may be made of glass, metal, ceramics, polymers, or a combination thereof including composite materials. In one embodiment the substrate is metal or alloy foil containing as non-limiting examples molybdenum, aluminum, titanium, iron, copper, tungsten, steel or combinations thereof. In another embodiment the metal or alloy foil is coated with an ion diffusion barrier and / or an insulating layer succeeded by a conductive layer. In another embodiment the substrate is polymeric foil with a metallic or other conductive layer, e.g., transparent conductive oxide, carbon) deposited on the top of it. In one preferred embodiment, regardless of the nature of the underlying substrate material or materials, the surface contacting the liquid layer contains molybdenum.

[0050]After a liquid layer of the ink is deposited on the surface of the substrate, the solvent is subjected to evaporation by means of exposure to ambient or controlled atmosphere or vacuum that may be accompanied with a thermal treatment, referred to as preliminary anneal, to fabricate substrate coated with a hybrid precursor including discrete particles and surrounding media. This surrounding media is formed by solidification of the dissolved component.

Problems solved by technology

However, photovoltaic cells with kesterites, even when produced using high cost vacuum-based methods, have so far achieved at best only <6.7 percent efficiencies, see Katagiri, H. et. al.

However, there are no reports of hydrazine-based deposition approaches of depositing homogeneous chalcogenide layers from dispersions of metal chalcogenides in systems that are not strictly soluble in hydrazine.

Further, there are no reports to extend the nanoparticle- and microparticle-based approaches to systems without organic binders in a manner that particle-based precursors can readily react with solution component and form large-grained films with good electrical characteristics.

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