The disclosed technology generally relates to chalcogenide thin films, and more particularly to ternary and quaternary chalcogenide thin films having a wide band-gap, and further relates to photovoltaic cells containing such thin films, e.g., as an absorber layer. In one aspect, a method of forming a ternary or quaternary thin film chalcogenide layer containing Cu and Si comprises depositing a copper layer on a substrate. The method additionally comprises depositing a silicon layer on the copper layer with a [Cu]/[Si] atomic ratio of at least 0.7, and thereafter annealing in an inert atmosphere. The method further includes performing a first selenization or a first sulfurization, thereby forming a ternary thin film chalcogenide layer on the substrate. In another aspect, a composite structure includes a substrate having a service temperature not exceeding 600 C. and a ternary chalcogenide thin film or a quaternary chalcogenide thin film on the substrate, where the ternary or quaternary chalcogenide thin film comprises a selenide and/or a sulfide containing Cu and Si.

A multilayer stack including a substrate, an active layer, and a tetradymite buffer layer positioned between the substrate and the active layer is disclosed. A method for fabricating a multilayer stack including a substrate, a tetradymite buffer layer and an active layer is also disclosed. Use of such stacks may be in photovoltaics, solar cells, light emitting diodes, and night vision arrays, among other applications.

A method for fabricating a photovoltaic device includes forming a polycrystalline absorber layer including CuZnSnS(Se) (CZTSSe) over a substrate. The absorber layer is rapid thermal annealed in a sealed chamber having elemental sulfur within the chamber. A sulfur content profile is graded in the absorber layer in accordance with a size of the elemental sulfur and an anneal temperature to provide a graduated bandgap profile for the absorber layer. Additional layers are formed on the absorber layer to complete the photovoltaic device.

There is provided a quantum dot solar cell having a high optical absorption coefficient. The quantum dot solar cell includes a quantum dot layer 3 including a plurality of quantum dots 1, wherein the quantum dot layer 3 includes a first quantum dot layer 3A having an index /x of 5% or more, wherein x is an average particle size, and is a standard deviation. The quantum dot layer 3 also includes a second quantum dot layer 3B that is provided on the light entrance surface 3b and/or the light exit surface 3c of the first quantum dot layer 3A and has an average particle size and an index /x smaller than those of the first quantum dot layer 3A.

A method for forming a photovoltaic device includes forming a photovoltaic absorption stack on a substrate including one or more of I-III-VI.sub.2 and I.sub.2-II-IV-VI.sub.4 semiconductor material. A transparent conductive contact layer is deposited on the photovoltaic absorption stack at a temperature less than 200 degrees Celsius. The transparent conductive contact layer has a thickness of about one micron and is formed on a front light-receiving surface. The surface includes pyramidal structures due to an as deposited thickness. The transparent conductive contact layer is wet etched to further roughen the front light-receiving surface to reduce reflectance.

A method for forming a thin film having sulfide single-crystal nanoparticles includes dropping a sulfide precursor solution on the surface of a Group VI absorption layer, and then performing thermal decomposition on the sulfide precursor solution under a predetermined temperature to form a thin film consisting of sulfide single-crystal nanoparticles on the surface of the Group VI absorption layer.

Techniques for forming an ohmic back contact for Ag.sub.2ZnSn(S,Se).sub.4 photovoltaic devices. In one aspect, a method for forming a photovoltaic device includes the steps of: depositing a refractory electrode material onto a substrate; depositing a contact material onto the refractory electrode material, wherein the contact material includes a transition metal oxide; forming an absorber layer on the contact material, wherein the absorber layer includes Ag, Zn, Sn, and at least one of S and Se; annealing the absorber layer; forming a buffer layer on the absorber layer; and forming a top electrode on the buffer layer. The refractory electrode material may be Mo, W, Pt, Ti, TiN, FTO, and combinations thereof. The transition metal oxide may be TiO.sub.2, ZnO, SnO, ZnSnO, Ga.sub.2O.sub.3, and combinations thereof. A photovoltaic device is also provided.

A photovoltaic device and a method of making a photovoltaic device that includes a stack of layers, including a substrate and an electrode layer. The photovoltaic device includes a semiconductor light absorption layer that is formed on the stack by a coating liquid that includes a plurality of semiconducting particles. The coating liquid may also include a solvent and a plurality of additive molecules. The photovoltaic device also includes a transparent conducting layer disposed on the semiconductor light absorption layer and a grid electrode disposed on the transparent conducting layer.

A concrete having a smooth surface, which is wholly or partly coated with a polymer film obtained by polymerisation under the action of radiation, where the film is itself wholly or partly coated with a thin photovoltaic film.

Photovoltaic devices based on an Ag.sub.2ZnSn(S,Se).sub.4 (AZTSSe) absorber and techniques for formation thereof are provided. In one aspect, a method for forming a photovoltaic device includes the steps of: coating a substrate with a conductive layer; contacting the substrate with an Ag source, a Zn source, a Sn source, and at least one of a S source and a Se source under conditions sufficient to form an absorber layer on the conductive layer having Ag, Zn, Sn, and at least one of S and Se; and annealing the absorber layer. Methods of doping the AZTSSe are provided. A photovoltaic device is also provided.