Techniques for increasing grain size in AZTSSe absorber materials are provided. In one aspect, a method for forming an absorber film on a substrate includes: contacting the substrate with an Ag source, a Zn source, a Sn source, and an S source and/or an Se source under conditions sufficient to form the absorber film on the substrate having a target composition of: Ag.sub.XZn.sub.YSn(S,Se).sub.Z, wherein 1.7<x<2.2, 0.9<y<1.3, and 3.5<z<4.5, and including an amount of the Ag source that is from about 10% to about 30% greater than is needed to achieve the target composition; annealing the absorber film; and removing excess Ag from the absorber film. A solar cell and method for fabrication thereof are also provided.

In various embodiments, evaporation sources are heated and/or cooled via a fluid-based thermal management system during deposition of thin films.

A photovoltaic device includes a first contact layer formed on a substrate. An absorber layer includes CuZnSnS(Se) (CZTSSe) on the first contact layer. A buffer layer is formed in contact with the absorber layer. Metal dopants are dispersed in a junction region between the absorber layer and the buffer layer. The metal dopants have a valence between the absorber layer and the buffer layer to increase junction potential. A transparent conductive contact layer is formed over the buffer layer.

Disclosed are metal chalcogenide nanoparticles forming a light absorption layer of solar cells including a first phase including copper (Cu)-tin (Sn) chalcogenide and a second phase including zinc (Zn) chalcogenide, and a method of preparing the same.

A method of preparing a Ag.sub.2ZnSn(S,Se).sub.4 compound, including dissolving selenourea (SeC(NH.sub.2).sub.2) in an aprotic solvent, and dissolving a silver salt, a zinc salt, and a tin salt in the aprotic solvent with the selenourea to form a metal solution; and coating the metal solution onto a substrate to form an Ag.sub.2ZnSn(S,Se).sub.4 compound layer on the substrate.

The present invention provides a 3-dimensional P-N junction solar cell composed of a base board coated with a back plate on the upper face of the same; a P type semiconductor thin film formed on the top side of the back plate which has a 3-dimensional porous structure and is composed of P type semiconductor crystal grains; a N type buffer layer formed on the surface of the crystal grains of the said P type semiconductor thin film with playing a role of coating the thin film; and a transparent electrode formed on the surface of the crystal grains of the P type semiconductor thin film on which the N type buffer layer is formed. The solar cell of the present invention is a P-N junction solar cell including a 3-dimensional photo catalytic thin film, which can provide an improved photoelectric conversion efficiency, compared with the conventional P-N junction solar cell, owing to the formation of the N-type buffer layer on the surface of the crystal grains of the 3-dimensional P type semiconductor thin film.

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.

A photovoltaic device includes a substrate, a first electrode formed on the substrate and a p-type absorber layer including a chalcogenide compound. An n-type layer includes a zinc oxysulfide material having a sulfur content adjusted to match a feature of the absorber layer. A transparent contact is formed on the n-type layer.

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.

Techniques for fabrication of kesterite CuZnSn(Se,S) films and improved photovoltaic devices based on these films are provided. In one aspect, a method of fabricating a kesterite film having a formula Cu.sub.2xZn.sub.1+ySn(S.sub.1zSe.sub.z).sub.4+q, wherein 0x1; 0y1; 0z1; and 1q1 is provided. The method includes the following steps. A substrate is provided. A bulk precursor layer is formed on the substrate, the bulk precursor layer comprising Cu, Zn, Sn and at least one of S and Se. A capping layer is formed on the bulk precursor layer, the capping layer comprising at least one of Sn, S and Se. The bulk precursor layer and the capping layer are annealed under conditions sufficient to produce the kesterite film having values of x, y, z and q for any given part of the film that deviate from average values of x, y, z and q throughout the film by less than 20 percent.