A photovoltaic device includes a substrate, a back contact layer disposed above the substrate, and an absorber layer disposed above the back contact layer. The absorber layer includes at least two regions at respectively different horizontally locations. Each respective region has a respectively different concentration profile of an ingredient at a respective depth of the absorber layer.

A multijunction solar cell assembly of two or more spatially split solar cell subassemblies, each of which includes a respective monolithic semiconductor body composed of a tandem stack of solar subcells, where the subassemblies are interconnected electrically to one another so that a series electrical circuit is formed between groups of one or more subcells in each subassembly. In some cases, relatively high band gap semiconductor materials can be used for the upper subcells. The solar cell assemblies can be particularly advantageous for applications in space.

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.

The present invention provides a CIGS film substantially free from oxidation of a front surface thereof and a CIGS solar cell employing the CIGS film and substantially free from reduction and variation in conversion efficiency. The CIGS film, which is used as a light absorbing layer for the CIGS solar cell, includes: a first region having a Ga/(In+Ga) ratio progressively reduced along its thickness toward a predetermined first thickness position from a back surface of the CIGS film; a second region having a Ga/(In+Ga) ratio progressively increased along its thickness toward a predetermined second thickness position from the first region; and a third region provided on the second region and having a Ga/(In+Ga) ratio progressively reduced along its thickness toward the front surface of the CIGS film.

A system and method of patterning dopants of opposite polarity to form a solar cell is described. Two dopant films are deposited on a substrate. A laser is used to pattern the N-type dopant, by mixing the two dopant films into a single film with an exposure to the laser and/or drive the N-type dopant into the substrate to form an N-type emitter. A thermal process drives the P-type dopant from the P-type dopant film to form P-type emitters and further drives the N-type dopant from the single film to either form or further drive the N-type emitter.

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.

This solar cell is provided with a substrate (11), a first electrode layer (12) which is arranged on the substrate (11), a p-type CZTS light absorption layer (13) which is arranged on the first electrode layer (12) and which contains copper, zinc, tin, and group VI elements including sulfur and selenium, and an n-type second electrode layer (15) which is arranged on the CZTS light absorption layer (13), wherein the sulfur concentration in the group VI elements in the CZTS light absorption layer (13) increases, in the depth direction, from the side facing the second electrode layer (15) towards the side facing the first electrode layer (12).

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.

Material and antireflection structure and methods of manufacturing are provided that produce efficient photovoltaic power conversion from thin film solar cells on flexible substrates. Step-graded antireflection structures are placed on the front of the device structure. Materials of different energy gap are combined in the depletion region of at least one of the semiconductor junctions within the thin film device structure. Conductive, low refractive index layers are deposited on the bottom of the thin film device structure to form an omni-directional back reflector contact.

A multijunction solar cell including an upper first solar subcell having a first band gap and positioned for receiving an incoming light beam; and a second solar subcell disposed below and adjacent to and lattice matched with said upper first solar subcell, and having a second band gap smaller than said first band gap; wherein at least one of the solar subcells has a graded band gap throughout the thickness of at least a portion of its emitter layer and base layer.