A photovoltaic device is presented. The photovoltaic device includes a layer stack; and an absorber layer is disposed on the layer stack. The absorber layer comprises selenium, wherein an atomic concentration of selenium varies across a thickness of the absorber layer. The photovoltaic device is substantially free of a cadmium sulfide layer.

A subtractive forming method that includes providing a material stack including a samarium and selenium containing layer and an aluminum containing layer in direct contact with the samarium and selenium containing layer. The samarium component of the samarium and selenium containing layer of the exposed portion of the material stack is etched with an etch chemistry comprising citric acid and hydrogen peroxide that is selective to the aluminum containing layer. The hydrogen peroxide reacts with the aluminum containing layer to provide an oxide etch protectant surface on the aluminum containing layer, and the citric acid etches samarium selectively to the oxide etch protectant surface. Thereafter, a remaining selenium component of is removed by elevating a temperature of the selenium component.

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.

Atomic layer deposition (ALD) processes for forming Te-containing thin films, such as SbTe, GeTe, GeSbTe, BiTe, and ZnTe thin films are provided. ALD processes are also provided for forming Se-containing thin films, such as SbSe, GeSe, GeSbSe, BiSe, and ZnSe thin films are also provided. Te and Se precursors of the formula (Te,Se)(SiR.sup.1R.sup.2R.sup.3).sub.2 are preferably used, wherein R.sup.1, R.sup.2, and R.sup.3 are alkyl groups. Methods are also provided for synthesizing these Te and Se precursors. Methods are also provided for using the Te and Se thin films in phase change memory devices.

A method for manufacturing a semiconductor substrate according to the present invention includes preparing a seed substrate containing a semiconductor material, forming an ion implanted layer at a certain depth from a front surface of a main surface of the seed substrate by implanting ions into the seed substrate, growing a semiconductor layer on the main surface of the seed substrate with a vapor-phase synthesis method, and separating a semiconductor substrate including the semiconductor layer and a part of the seed substrate by irradiating the front surface of the main surface of at least any of the semiconductor layer and the seed substrate with light.

A hybrid vapor phase-solution phase CZT(S,Se) growth technique is provided. In one aspect, a method of forming a kesterite absorber material on a substrate includes the steps of: depositing a layer of a first kesterite material on the substrate using a vapor phase deposition process, wherein the first kesterite material includes Cu, Zn, Sn, and at least one of S and Se; annealing the first kesterite material to crystallize the first kesterite material; and depositing a layer of a second kesterite material on a side of the first kesterite material opposite the substrate using a solution phase deposition process, wherein the second kesterite material includes Cu, Zn, Sn, and at least one of S and Se, wherein the first kesterite material and the second kesterite material form a multi-layer stack of the absorber material on the substrate. A photovoltaic device and method of formation thereof are also provided.

A subtractive forming method that includes providing a material stack including a samarium and selenium containing layer and an aluminum containing layer in direct contact with the samarium and selenium containing layer. The samarium component of the samarium and selenium containing layer of the exposed portion of the material stack is etched with an etch chemistry comprising citric acid and hydrogen peroxide that is selective to the aluminum containing layer. The hydrogen peroxide reacts with the aluminum containing layer to provide an oxide etch protectant surface on the aluminum containing layer, and the citric acid etches samarium selectively to the oxide etch protectant surface. Thereafter, a remaining selenium component of is removed by elevating a temperature of the selenium component.

Disclosed is a formulation of semiconductor nanoplatelets, including at least one nanoplatelet including a nanoplatelet core and a shell on the surface of the nanoplatelet core, wherein the formulation is substantially free of molecular oxygen and/or molecular water, and uses thereof.

A method of performing HVPE heteroepitaxy comprises exposing a substrate to a carrier gas, a first precursor gas, a Group II/III element, and ternary-forming gasses (V/VI group precursor), to form a heteroepitaxial growth of a binary, ternary, and/or quaternary compound on the substrate; wherein the carrier gas is H.sub.2, wherein the first precursor gas is HCl, the Group II/III element comprises at least one of Zn, Cd, Hg, Al, Ga, and In; and wherein the ternary-forming gasses comprise at least two or more of AsH.sub.3 (arsine), PH.sub.3 (phosphine), H.sub.2Se (hydrogen selenide), H.sub.2Te (hydrogen telluride), SbH.sub.3 (hydrogen antimonide, or antimony tri-hydride, or stibine), H.sub.2S (hydrogen sulfide), NH.sub.3 (ammonia), and HF (hydrogen fluoride); flowing the carrier gas over the Group II/III element; exposing the substrate to the ternary-forming gasses in a predetermined ratio of first ternary-forming gas to second ternary-forming gas (1tf:2tf ratio); and changing the 1tf:2tf ratio over time.

A hybrid vapor phase-solution phase CZT(S,Se) growth technique is provided. In one aspect, a method of forming a kesterite absorber material on a substrate includes the steps of: depositing a layer of a first kesterite material on the substrate using a vapor phase deposition process, wherein the first kesterite material includes Cu, Zn, Sn, and at least one of S and Se; annealing the first kesterite material to crystallize the first kesterite material; and depositing a layer of a second kesterite material on a side of the first kesterite material opposite the substrate using a solution phase deposition process, wherein the second kesterite material includes Cu, Zn, Sn, and at least one of S and Se, wherein the first kesterite material and the second kesterite material form a multi-layer stack of the absorber material on the substrate. A photovoltaic device and method of formation thereof are also provided.