Novel structures of photovoltaic cells are provided. The cells are based on nanometer or micrometer-scaled wires, tubes, and/or rods, which are made of electronic materials covering semiconductors, insulators, and may be metallic in structure. These photovoltaic cells have large power generation capability per unit physical area over the conventional cells. These cells will have enormous applications such as in space, commercial, residential and industrial applications.

Devices converting light to electricity (such as solar cells or photodetectors) including a heavily-doped p-type a-SiC.sub.y:H and an i-Mg.sub.xCd.sub.1xTe/n-CdTe/NMg.sub.0.24Cd.sub.0.76Te double heterostructure (DH), with power conversion efficiency of as high as 17%, V.sub.oc as high as 1.096 V, and all operational characteristics being substantially better than those of monocrystalline solar cells known to-date. The a-SiC.sub.y:H layer is configured to enable high built-in potential while, at the same time, allowing the doped absorber to maintain a very long carry lifetime. In comparison, similar undoped CdTe/Mg.sub.xCd.sub.1xTe DH designs reveal a long carrier lifetime of 3.6 s and an interface recommendation velocity of 1.2 cm/s, which are lower than the record values reported for GaAs/Al.sub.0.5Ga.sub.0.5As (18 cm/s) and GaAs/Ga.sub.0.5In.sub.0.5P (1.5 cm/s) DHs.

Devices converting light to electricity (such as solar cells or photodetectors) including a heavily-doped p-type a-SiC.sub.y:H and an i-Mg.sub.xCd.sub.1xTe/n-CdTe/NMg.sub.0.24Cd.sub.0.76Te double heterostructure (DH), with power conversion efficiency of as high as 17%, V.sub.oc as high as 1.096 V, and all operational characteristics being substantially better than those of monocrystalline solar cells known to-date. The a-SiC.sub.y:H layer is configured to enable high built-in potential while, at the same time, allowing the doped absorber to maintain a very long carry lifetime. In comparison, similar undoped CdTe/Mg.sub.xCd.sub.1xTe DH designs reveal a long carrier lifetime of 3.6 s and an interface recommendation velocity of 1.2 cm/s, which are lower than the record values reported for GaAs/Al.sub.0.5Ga.sub.0.5As (18 cm/s) and GaAs/Ga.sub.0.5In.sub.0.5P (1.5 cm/s) DHs.

Embodiments of a photovoltaic device are provided herein. The photovoltaic device can include a layer stack and an absorber layer disposed on the layer stack. The absorber layer can include a first region and a second region. Each of the first region of the absorber layer and the second region of the absorber layer can include a compound comprising cadmium, selenium, and tellurium. An atomic concentration of selenium can vary across the absorber layer. The first region of the absorber layer can have a thickness between 100 nanometers to 3000 nanometers. The second region of the absorber layer can have a thickness between 100 nanometers to 3000 nanometers. A ratio of an average atomic concentration of selenium in the first region of the absorber layer to an average atomic concentration of selenium in the second region of the absorber layer can be greater than 10.

Embodiments of a photovoltaic device are provided herein. The photovoltaic device can include a layer stack and an absorber layer disposed on the layer stack. The absorber layer can include a first region and a second region. Each of the first region of the absorber layer and the second region of the absorber layer can include a compound comprising cadmium, selenium, and tellurium. An atomic concentration of selenium can vary across the absorber layer. The first region of the absorber layer can have a thickness between 100 nanometers to 3000 nanometers. The second region of the absorber layer can have a thickness between 100 nanometers to 3000 nanometers. A ratio of an average atomic concentration of selenium in the first region of the absorber layer to an average atomic concentration of selenium in the second region of the absorber layer can be greater than 10.

A photovoltaic device includes a substrate structure and a p-type semiconductor absorber layer, the substrate structure including a CdSSe layer. A photovoltaic device may alternatively include a CdSeTe layer. A process for manufacturing a photovoltaic device includes forming a CdSSe layer over a substrate by at least one of sputtering, evaporation deposition, CVD, chemical bath deposition process, and vapor transport deposition process. The process includes forming a p-type absorber layer above the CdSSe layer.

A photovoltaic device includes a substrate structure and a p-type semiconductor absorber layer, the substrate structure including a CdSSe layer. A photovoltaic device may alternatively include a CdSeTe layer. A process for manufacturing a photovoltaic device includes forming a CdSSe layer over a substrate by at least one of sputtering, evaporation deposition, CVD, chemical bath deposition process, and vapor transport deposition process. The process includes forming a p-type absorber layer above the CdSSe layer.

The present invention proposes a method to form a gradient thin film using a spray pyrolysis technique. The method comprises providing a base substrate, preparing a spray aqueous solution by mixing at least two precursor compounds comprising at least two different elements and spraying the spray aqueous solution onto the base substrate. According to the present invention, the ratio of the concentration of the at least two different elements within the spray aqueous solution is varied while performing the method. In this way, a thin film having a gradient of elemental composition over its layer thickness may be formed.

The present invention proposes a method to form a gradient thin film using a spray pyrolysis technique. The method comprises providing a base substrate, preparing a spray aqueous solution by mixing at least two precursor compounds comprising at least two different elements and spraying the spray aqueous solution onto the base substrate. According to the present invention, the ratio of the concentration of the at least two different elements within the spray aqueous solution is varied while performing the method. In this way, a thin film having a gradient of elemental composition over its layer thickness may be formed.

A solar cell structure is disclosed that includes a first metal layer, formed over predefined portions of a sun-exposed major surface of a semiconductor structure, that form electrical gridlines of the solar cell; a network of carbon nanotubes formed over the first metal layer; and a second metal layer formed onto the network of carbon nanotubes, wherein the second metal layer infiltrates the network of carbon nanotubes to connect with the first metal layer to form a first metal matrix composite comprising a metal matrix and a carbon nanotube reinforcement, wherein the second metal layer is an electrically conductive layer in which the carbon nanotube reinforcement is embedded in and bonded to the metal matrix, and the first metal matrix composite provides enhanced mechanical support as well as enhanced or equal electrical conductivity for the electrical contacts against applied mechanical stressors to the electrical contacts.