A composition of matter, in particular a photovoltaic cell, comprising: at least one core semiconductor nanowire on a graphitic substrate, said at least one core nanowire having been grown epitaxially on said substrate wherein said nanowire comprises at least one group III-V compound or at least one group II-VI compound or at least one group IV element; a semiconductor shell surrounding said core nanowire, said shell comprising at least one group III-V compound or at least one group II-VI compound or at least one group IV element such that said core nanowire and said shell form a n-type semiconductor and a p-type semiconductor respectively or vice versa; and an outer conducting coating surrounding said shell which forms an electrode contact.

This invention relates to a novel structure of photovoltaic devices (e.g. photovoltaic cells also called as solar cells) are provided. The cells are based on the micro or nano scaled structures which could not only increase the surface area but also have the capability of reducing the reflection and increasing the absorption of incident light. More specifically, the structures are based on 3D structure which are made of electric materials covering semiconductors, insulators, dielectric, polymer, and metallic type materials. By using such structures reflection loss of the light from the cell is significantly reduced, increasing the absorption, which results in increasing the conversion efficiency of the solar cell, and reducing the usage of material while increasing the flexibility of the solar cell. The structures can be also used in other optical devices wherein the reflection loss and absorption are required to enhance significantly improve the device performances.

Described herein is a diffusion-based ex-situ group V element doping method in the CdCl.sub.2 heat-treated polycrystalline CdTe film. The ex-situ doping using group V halides, such as PCl.sub.3, AsCl.sub.3, SbCl.sub.3, or BiCl.sub.3, demonstrated a promising PCE of ˜18% and long-term light soaking stability in CdSe/CdTe and CdS/CdTe devices with decent carrier concentration>10.sup.15 cm.sup.−3. This ex-situ solution or vapor process can provide a low-cost alternative pathway for effective doping of As, as well as P, Sb, and Bi, in CdTe solar cells with limited deviation from the current CdTe manufacturing process.

Methods and devices are described for a photovoltaic device. The photovoltaic device includes a glass substrate, a semiconductor absorber layer formed over the glass substrate, a metal back contact layer formed over the semiconductor absorber layer, and a p-type back contact buffer layer formed from one of MnTe, Cd.sub.1-xMn.sub.xTe, and SnTe, the buffer layer disposed between the semiconductor absorber layer and the metal back contact layer.

Disclosed are a single-source precursor for synthesizing metal chalcogenide nanoparticles for producing a light absorption layer of solar cells comprising a Group VI element linked as a ligand to any one metal selected from the group consisting of copper (Cu), zinc (Zn) and tin (Sn), metal chalcogenide nanoparticles produced by heat-treating at least one type of the single-source precursor, a method of preparing the same, a thin film produced using the same and a method of producing the thin film.

A photovoltaic device is presented. The photovoltaic device includes a buffer layer disposed on a transparent conductive oxide layer; a window layer disposed on the buffer layer; and an interlayer interposed between the transparent conductive oxide layer and the window layer. The interlayer includes a metal species, wherein the metal species includes gadolinium, beryllium, calcium, barium, strontium, scandium, yttrium, hafnium, cerium, lutetium, lanthanum, or combinations thereof. A method of making a photovoltaic device is also presented

A layer of an n-type chalcogenide compositions provided on a substrate in the presence of an oxidizing gas in an amount sufficient to provide a resistivity to the layer that is less than the resistivity a layer deposited under identical conditions but in the substantial absence of oxygen.

The present invention relates to a method for preparing an aqueous or hydro-alcoholic colloidal solution of metal chalcogenide amorphous nanoparticles notably of the Cu.sub.2ZnSnS.sub.4 (CZTS) type and to the obtained colloidal solution. The present invention also relates to a method for manufacturing a film of large-grain crystallized semi-conducting metal chalcogenide film notably of CZTS obtained from an aqueous or hydro-alcoholic colloidal solution according to the invention, said film being useful as an absorption layer deposited on a substrate applied in a solid photovoltaic device.

A solar cell includes a doped CdTe layer; a graphene layer over the CdTe layer; and metal contacts over the graphene layer. Advantageously, the metal contacts are composed of Pt or MoO.sub.3-x. The doped CdTe layer can be composed of a p-doped CdTe layer, and the solar cell comprises an n-doped CdS layer beneath the CdTe layer. The solar cell can include a conducting oxide layer beneath the CdS layer. The conducting oxide layer can be composed of SnO.sub.2:F. The solar cell can include a glass layer beneath the conducting oxide layer. The graphene contacting the MoO contacts particularly alleviates the issue of the inability of prior CdTe solar cells to collect holes and could increase efficiency by about 5%.

Designs of extremely high efficiency solar cells are described. A novel alternating bias scheme enhances the photovoltaic power extraction capability above the cell band-gap by enabling the extraction of hot carriers. When applied in conventional solar cells, this alternating bias scheme has the potential of more than doubling their yielded net efficiency. When applied in conjunction with solar cells incorporating quantum wells (QWs) or quantum dots (QDs) based solar cells, the described alternating bias scheme has the potential of extending such solar cell power extraction coverage, possibly across the entire solar spectrum, thus enabling unprecedented solar power extraction efficiency. Within such cells, a novel alternating bias scheme extends the cell energy conversion capability above the cell material band-gap while the quantum confinement structures are used to extend the cell energy conversion capability below the cell band-gap. Light confinement cavities are incorporated into the cell structure in order to allow the absorption of the cell internal photo emission, thus further enhancing the cell efficiency.