Provided are a solar cell and a light emitting device with low leakage current and low cost, using ZnO fine particles. A p-type ZnO layer (p-type layer) (14) made primarily of p-type ZnO fine particles (931) is formed. P-side electrodes (16) are formed at a plurality of regions on the p-type layer (14). A thin insulating layer (18) is formed between an n-type layer (13) and the p-type layer (14). In the insulating layer (18), openings are formed at regions A each not overlapping the p-side electrodes (16) and being apart from them in a plan view. In the configuration, by thus making the p-side electrodes (16) apart from the regions A, the length of a current path in the p-type layer (14) can be made substantially larger than the layer thickness. Accordingly, even when n-type ZnO fine particles (932) are incorporated in the p-type layer (14), it is possible to interpose some of the p-type ZnO fine particles (931) along a leakage current path caused by the incorporation, and thereby cut off the current path.

A perovskite-silicon tandem cell capable of absorbing solar radiation with energy lower than that of 1.12 eV, i.e., the bandgap of crystalline silicon—corresponding to the wavelength of 1100 nm. Ho.sup.3+ can absorb photons of wavelength range 1120 to 1190 nm, Tm.sup.3+, 1190 to 1260 nm, and Er.sup.3+, 1145 to 1580 nm, but up-conversion can be achieved using Ho.sup.3+, Tm.sup.3+, and Er.sup.3+-doped metal oxide, such as ZrO.sub.2, in perovskite-silicon tandem solar cells. Doped metal oxides, such as ZrO.sub.2 can also work as selective contacts. Such perovskite-silicon tandem structures can achieve over 30% solar energy conversion efficiency.

A perovskite-silicon tandem cell capable of absorbing solar radiation with energy lower than that of 1.12 eV, i.e., the bandgap of crystalline silicon—corresponding to the wavelength of 1100 nm. Ho.sup.3+ can absorb photons of wavelength range 1120 to 1190 nm, Tm.sup.3+, 1190 to 1260 nm, and Er.sup.3+, 1145 to 1580 nm, but up-conversion can be achieved using Ho.sup.3+, Tm.sup.3+, and Er.sup.3+-doped metal oxide, such as ZrO.sub.2, in perovskite-silicon tandem solar cells. Doped metal oxides, such as ZrO.sub.2 can also work as selective contacts. Such perovskite-silicon tandem structures can achieve over 30% solar energy conversion efficiency.

A photovoltaic device (100) can include an absorber layer (160). The absorber layer (160) 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 (160) can include oxygen in a central region of the absorber layer (160). The absorber layer (160) can include an alkali metal in the central region of the absorber layer (160). Methods for carrier activation can include exposing an absorber layer (160) to an annealing compound in a reducing environment (220). The annealing compound (224) can include cadmium chloride and an alkali metal chloride.

A photovoltaic device (100) can include an absorber layer (160). The absorber layer (160) 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 (160) can include oxygen in a central region of the absorber layer (160). The absorber layer (160) can include an alkali metal in the central region of the absorber layer (160). Methods for carrier activation can include exposing an absorber layer (160) to an annealing compound in a reducing environment (220). The annealing compound (224) can include cadmium chloride and an alkali metal chloride.

A photovoltaic device is described, the device comprising a transparent conducting electrode layer; a back contact layer comprising at least one MXene material; and an active layer, comprising a photovoltaic active material, disposed between the transparent conducting electrode layer and the back contact layer. Also described is a method of producing a photovoltaic device, the method comprising the steps of providing substrate, depositing a transparent conducting electrode over the substrate; depositing an active layer comprising a photovoltaic material over the transparent conducting electrode; and depositing an MXene layer material over the active layer. A method of generating electricity using the disclosed device is also described.

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.

The present invention proposes a method to form a CdSeTe thin film with a defined amount of selenium and with a high quality. The method comprises the steps of providing a base substrate and of depositing a partial CdSeTe layer on a first portion of the base substrate. The step of depositing a partial CdSeTe layer is performed at least twice, wherein a predetermined time period without deposition of a partial CdSeTe layer on the first portion of the base substrate is provided between two subsequent steps of depositing a partial CdSeTe layer. The temperature of the base substrate and the CdSeTe layer already deposited on the first portion of the base substrate is controlled during the predetermined time period such that re-evaporation of Cd and/or Te from the CdSeTe layer already deposited takes place.

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.