According to the embodiments provided herein, a photovoltaic device can include an absorber layer. The absorber layer can be doped p-type with a Group V dopant and can have a carrier concentration of the Group V dopant greater than 4×10.sup.15 cm.sup.−3. The absorber layer can include oxygen in a central region of the absorber layer. The absorber layer can include an alkali metal in the central region of the absorber layer. Methods for carrier activation can include exposing an absorber layer to an annealing compound in a reducing environment. The annealing compound can include cadmium chloride and an alkali metal chloride.

Mercury cadmium telluride (MCT) dual band photodiode elements are described that include an n-type barrier region interposed between first and second p-type regions. The first p-type region is arranged to absorb different IR wavelengths to the second p-type region in order that the photodiode element can sense two IR bands. A portion of the second p-type region is type converted using ion-beam milling to produce a n-type region that interfaces with the second p-type region and the n-type barrier region.

In one aspect, a method includes forming an electrical path between p-type mercury cadmium telluride and a metal layer. The forming of the electrical path includes depositing a layer of polycrystalline p-type silicon directly on to the p-type mercury cadmium telluride and forming the metal layer on the layer of polycrystalline p-type silicon. In another aspect, an apparatus includes an electrical path. The electrical path includes a p-type mercury cadmium telluride layer, a polycrystalline p-type silicon layer in direct contact with the p-type mercury cadmium telluride layer, a metal silicide in direct contact with the polycrystalline p-type silicon layer, and an electrically conductive metal on the metal silicide. In operation, holes, indicative of electrical current on the electrical path, flow from the p-type mercury cadmium telluride layer to the electrically conductive metal.

Photo-detection device (100) including a semiconductor substrate (110) made of Cd.sub.xHg.sub.1-xTe, with an N-doped region (120), a P-doped region (130), and a concentrated casing (150) only located in the P-doped region and having an average cadmium concentration greater than the average cadmium concentration in the N-doped region. According to the invention, the concentrated casing (150) has a cadmium concentration gradient, defining therein at least one intermediate gap zone (151) and at least one high gap zone (152), and the intermediate gap zone (151) is in direct physical contact with an electrical contact block (170). A significant reduction in the dark current and an optimal charge carrier collection are thus combined.

The present disclosure relates to thin-film solar cells with improved efficiency and methods for producing thin-film solar cells having increased efficiency. In certain embodiments, thin-film solar cells having an efficiency of over 21%, over 20%, over 19%, over 15%, over 10%, etc. has been obtained using the methods of the disclosure. In certain aspects, the methods of the disclosure use passivation, passivating oxides, and/or doping treatments in increase the efficiency of the thin-film solar cells; e.g., CdTe-based thin-film solar cells.

The invention relates to methods for preparing 3-element semiconductor nanocrystals of the formula WYxZ(1-x), wherein W is a Group II element, Y and Z are different Group VI elements, and 0<X<1, comprising dissolving a Group II element, a first Group VI element, and a second Group VI element in a one or more solvents. The Group II, VI and VI elements are combined to provide a II:VI:VI SCN precursor solution, which is heated to a temperature sufficient to produce semiconductor nanocrystals of the formula WYxZ(1-x). The solvent used to dissolve the Group II element comprises octadecene and a fatty acid. The solvent used to dissolve the Group VI elements comprises octadecene. The invention also includes semiconductor nanocrystals prepared according to the disclosed methods, as well as methods of using the semiconductor nanocrystals.

A method of fabricating a solid state radiation detector method includes mechanically lapping and polishing the first and the second surfaces of a semiconductor wafer using a plurality of lapping and polishing steps. The method also includes growing passivation oxide layers by use of oxygen plasma on the top of the polished first and second surfaces in order to passivate the semiconductor wafer. Anode contacts are deposited and patterned on top of the first passivation oxide layer, which is on top of the first surface. Cathode contacts, which are either monolithic or patterned, are deposited on top of the second passivation oxide layer, which is on the second surface. Aluminum nitride encapsulation layer can be deposited over the anode contacts and patterned to encapsulate the first passivation oxide layer, while physically exposing a center portion of each anode contact to electrically connect the anode contacts.

A photodetector comprising a photoabsorber, comprising a doped semiconductor, a contact layer comprising a doped semiconductor and a barrier layer comprising a charge carrier compensated semiconductor, the barrier layer compensated by doping impurities such that it exhibits a valence band energy level substantially equal to the valence band energy level of the photo absorbing layer and a conduction band energy level exhibiting a significant band gap in relation to the conduction band of the photo absorbing layer, the barrier layer disposed between the photoabsorber and contact layers. The relationship between the photo absorbing layer and contact layer valence and conduction band energies and the barrier layer conduction and valance band energies is selected to facilitate minority carrier current flow while inhibiting majority carrier current flow between the contact and photo absorbing layers.

A method of creating cadmium telluride films is presented. The method demonstrates heterogeneous nucleation of CdTe directly on a substrate through sequential deposition of aqueous precursor solutions containing cadmium and telluride ions, respectively. The method can include (i) applying a cadmium precursor solution to the substrate to form a cadmium precursor film on the substrate, (ii) applying a telluride precursor solution to the cadmium precursor film. The telluride precursor solution includes Te.sup.2− in solution such that a CdTe film is adherently formed directly on the substrate.

A photovoltaic device is disclosed including at least one Cadmium Sulfide Telluride (CdS.sub.xTe.sub.1−x) layer as are methods of forming such a photovoltaic device.