Abstract: Photoconversion devices comprising a semiconductor region of nanostructured crystalline material are disclosed. The nanostructures of a crystalline material provide for the generation of multiple excitons per photon absorbed by the crystalline nanostructure in response to incident solar radiation. The photoconversion devices will also include one or more optical elements providing for the concentration of sunlight in the semiconductor region. Also disclosed are photoconversion methods, systems and apparatus featuring the combination solar concentration with nanostructures of a crystalline material providing for the generation of multiple excitons per photon absorbed by the crystalline nanostructure in response to incident solar radiation.

Abstract: Solar cells and methods for use and making these solar cells are disclosed. An exemplary solar cell includes a first electrode. The solar cell also includes a nanocrystal film of a single material disposed in contact with the first electrode. The solar cell also includes a second electrode disposed in contact with the nanocrystal film, not in contact with the first electrode.

Abstract: A superlattice or multiple-quantum-well semiconductor is used as a photoelectrode in a photoelectrochemical process for converting solar energy into useful fuels or chemicals. The quantum minibands of the superlattice or multiple-quantum-well semiconductor effectively capture hot-charge carriers at or near their discrete quantum energies and deliver them to drive a chemical reaction in an electrolyte. The hot-charge carries can be injected into the electrolyte at or near the various discrete multiple energy levels quantum minibands, or they can be equilibrated among themselves to a hot-carrier pool and then injected into the electrolyte at one average energy that is higher than the lowest quantum band gap in the semiconductor.

Abstract: A system for the photoenhanced reduction of nitrogen. A p-type semiconductor cathode with a band gap between about 0.8 and 3.0 eV is irradiated with light falling within such energy range. The cathode is in contact with an electrolyte and capable of injecting photogenerated electrons into the electrolyte. An anode provides for removal of the resulting holes from the cathode. Cathode and anode are short circuited. For nitrogen molecule reduction, the electrolyte solution contains a chemical species capable in reduced form of chemically binding molecular nitrogen and of facilitating a series of reduction steps on the nitrogen. Specifically, such a chemical species is titanium isopropoxide.

Abstract: Photochemical diodes are provided which use light to drive both endoergic and exoergic chemical reactions such that optical energy is converted into chemical energy. The photochemical diodes are typically suspended in a bulk volume matrix of the constituent chemical reactants. The photochemical diodes, in the form of either Schottky-type diodes or p-n type diodes, are employed, for example, to convert water into hydrogen plus oxygen (or hydrogen peroxide); to convert hydrogen sulfide into hydrogen plus sulfur; and to photo-catalyze chemical reactions. The photochemical diodes of the invention comprise two portions, a first portion comprising an appropriately doped semiconductor material of a given conductivity and provided with an ohmic contact and a second portion comprising either metal (Schottky-type) or an appropriately doped semiconductor material of a conductivity type opposite to that of the first portion and provided with an ohmic contact (p-n type).

Abstract: Photoelectrolysis of water by solar radiation to produce hydrogen is achieved using semiconducting thin film electrodes. The cell comprises (a) an anodic electrode comprising at least one thin n-type semiconducting layer which has a bandgap ranging from about 0.5 to 4.0 eV and which is disposed on a supporting conductive substrate; (b) a cathodic counter-electrode comprising at least one thin p-type semiconducting layer which has a bandgap ranging from about 0.5 to 4.0 eV and which is supported on a supporting conductive substrate, the p-type layer adjacent the n-type layer being such that incident solar radiation impinges substantially simultaneously on both the n- and p-type electrodes; (c) means for retaining an electrolyte in contact with the exposed surfaces of the n- and p-type semiconducting electrodes; (d) external bias means between the electrode and the counter-electrode for biasing the cell with from 0 to about 1 V; and (e) means for collecting hydrogen and any oxidation products produced.