A composite material is described. The composite material comprises semiconductor nanocrystals, and organic molecules that passivate the surfaces of the semiconductor nanocrystals. One or more properties of the organic molecules facilitate the transfer of charge between the semiconductor nanocrystals. A semiconductor material is described that comprises p-type semiconductor material including semiconductor nanocrystals. At least one property of the semiconductor material results in a mobility of electrons in the semiconductor material being greater than or equal to a mobility of holes. A semiconductor material is described that comprises n-type semiconductor material including semiconductor nanocrystals. At least one property of the semiconductor material results in a mobility of holes in the semiconductor material being greater than or equal to a mobility of electrons.

An embodiment avalanche photodiode includes a substrate, an n-type contact layer, a buffer layer, a multiplication layer, a field-control layer, an absorption layer, and a p-type contact layer. A conductive layer is formed in a central part of the buffer layer. The substrate is constituted of a semiconductor with a higher thermal conductivity than InP such as SiC, and the n-type contact layer is constituted of a same semiconductor as the substrate and is made n-type.

An embodiment avalanche photodiode includes a substrate, an n-type contact layer, a buffer layer, a multiplication layer, a field-control layer, an absorption layer, and a p-type contact layer. A conductive layer is formed in a central part of the buffer layer. The substrate is constituted of a semiconductor with a higher thermal conductivity than InP such as SiC, and the n-type contact layer is constituted of a same semiconductor as the substrate and is made n-type.

This infrared detection element includes a buffer layer (InAsSb layer) 3, a buffer layer (InAs layer) 4, and a light absorption layer (InAsSb layer) 5. A critical film thickness hc of the InAs layer satisfies a relation of hc<t with a thickness t of the InAs layer. In this case, it is possible to improve crystallinities of the buffer layer 4 of InAs and the light absorption layer 5 of InAsSb formed on the buffer layer 3.

This infrared detection element includes a buffer layer (InAsSb layer) 3, a buffer layer (InAs layer) 4, and a light absorption layer (InAsSb layer) 5. A critical film thickness hc of the InAs layer satisfies a relation of hc<t with a thickness t of the InAs layer. In this case, it is possible to improve crystallinities of the buffer layer 4 of InAs and the light absorption layer 5 of InAsSb formed on the buffer layer 3.

Systems and methods are provided for fabricating pyrite thin films from molecular inks. A process is provided that comprises dissolving simple iron-bearing and sulfur-bearing molecules in an appropriate solvent and then depositing the solution onto an appropriate substrate using one of several methods (roll-to-roll coating, spraying, spin coating, etc.), resulting in a solid film consisting of the molecules. These molecular precursor films are then heated to 200-600° C. in the presence of sulfur-bearing gases (e.g., S.sub.2, H.sub.2S) to convert the molecular films into films of crystalline iron pyrite (FeS.sub.2).

Systems and methods are provided for fabricating pyrite thin films from molecular inks. A process is provided that comprises dissolving simple iron-bearing and sulfur-bearing molecules in an appropriate solvent and then depositing the solution onto an appropriate substrate using one of several methods (roll-to-roll coating, spraying, spin coating, etc.), resulting in a solid film consisting of the molecules. These molecular precursor films are then heated to 200-600° C. in the presence of sulfur-bearing gases (e.g., S.sub.2, H.sub.2S) to convert the molecular films into films of crystalline iron pyrite (FeS.sub.2).

Disclosed are a mercury cadmium telluride-black phosphorus van der Waals heterojunction infrared polarization detector and a preparation method thereof. The structure of the detector from bottom to top comprises a substrate, a mercury cadmium telluride material, an insulating layer, a two-dimensional semiconductor black phosphorus, and metal electrodes. First, growing the mercury cadmium telluride material on the substrate, removing part of the mercury cadmium telluride by ultraviolet lithography and argon ion etching, filling with aluminum oxide as the insulating layer using an electron beam evaporation method, transferring the two-dimensional semiconductor material black phosphorus at the junction of mercury cadmium telluride and an insulating layer assisted by a polypropylene carbonate film, and preparing the metal source-drain electrodes by electron beam lithography technology combined with the lift-off process to form the mercury cadmium telluride-black phosphorus van der Waals heterojunction infrared polarization detector.

Disclosed are a mercury cadmium telluride-black phosphorus van der Waals heterojunction infrared polarization detector and a preparation method thereof. The structure of the detector from bottom to top comprises a substrate, a mercury cadmium telluride material, an insulating layer, a two-dimensional semiconductor black phosphorus, and metal electrodes. First, growing the mercury cadmium telluride material on the substrate, removing part of the mercury cadmium telluride by ultraviolet lithography and argon ion etching, filling with aluminum oxide as the insulating layer using an electron beam evaporation method, transferring the two-dimensional semiconductor material black phosphorus at the junction of mercury cadmium telluride and an insulating layer assisted by a polypropylene carbonate film, and preparing the metal source-drain electrodes by electron beam lithography technology combined with the lift-off process to form the mercury cadmium telluride-black phosphorus van der Waals heterojunction infrared polarization detector.

A solar cell of an embodiment includes: a transparent substrate; a p-electrode on the substrate, the p-electrode including a first p-electrode containing an Sn-based metal oxide, a second p-electrode having an opening and consisting of a wiring containing a metal or graphene, and a third p-electrode containing an In-based metal oxide; a p-type light absorbing layer in direct contact with a surface of the first p-electrode on a side opposite to the second p-electrode side; an n-type layer provided on the p-type light absorbing layer; and an n-electrode provided on the n-type layer. The third p-electrode is provided to be present between the first p-electrode and the second p-electrode and to be in direct contact with an upper surface of the second p-electrode. An entire side surface of the second p-electrode is in direct contact with the first p-electrode.