Techniques for achieving band gap grading in CZTS/Se absorber materials are provided. In one aspect, a method for creating band gap grading in a CZTS/Se absorber layer includes the steps of: providing a reservoir material containing Si or Ge; forming the CZTS/Se absorber layer on the reservoir material; and annealing the reservoir material and the CZTS/Se absorber layer under conditions sufficient to diffuse Si or Ge atoms from the reservoir material into the CZTS/Se absorber layer with a concentration gradient to create band gap grading in the CZTS/Se absorber layer. A photovoltaic device and method of forming the photovoltaic device are also provided.

Disclosed is a solar cell including a substrate, an electrode layer disposed on the substrate, a p-type light-absorption layer disposed on the electrode layer, an n-type ZnS layer disposed on the p-type light-absorption layer, and a transparent electrode layer disposed on the n-type ZnS layer. The substrate can be immersed into an acidic solution of zinc salt, chelate, and thioacetamide, thereby forming the n-type ZnS layer on the substrate.

A photovoltaic cell can include a substrate having a copper-doped semiconductor layer. The doping can be mediated with a salt.

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.

Disclosed herein are compositions and methods for making polycrystalline thin films having very large grains sizes and exhibiting improved properties over existing thin films.

A method for producing, apparatus for producing and photovoltaic device including semiconductor layers with halide heat treated surfaces that increase grain growth within at least one of the semiconductor layers and improve the interface between the semiconductor layers. The halide heat treatment includes applying and heating multiple coatings of a halide compound on surfaces adjacent to or part of the semiconductor layers.

A thin film structure according to various example embodiments includes a first buffer layer, a transition metal dichalcogenide layer on the first buffer layer, and a second buffer layer on the transition metal dichalcogenide layer, wherein the second buffer layer includes same chalcogen element as a chalcogen element included in the transition metal dichalcogenide layer.