Solar cell structures comprising a plurality of solar cells, wherein each solar cell is separated from adjacent solar cell via a tunnel junction and/or a resonant tunneling structure (RTS), are described. Solar cells are implemented on Ge, Si, GaN, sapphire, and glass substrates. Each of the plurality of solar cells is at least partially constructed from a cell material which harnesses photons having energies in a predetermined energy range. In one embodiment each solar cell comprises of at least two sub-cells. It also describes a nano-patterned region/layer to implement high efficiency tandem/multi-junction solar cells that reduces dislocation density due to mismatch in lattice constants in the case of single crystalline and/or polycrystalline solar cells. Finally, solar structure could be used as light-emitting diodes when biased in forward biasing mode. The mode of operation could be determined by a programmed microprocessor.

Disclosed herein are methods for exfoliation of single crystals allowing for growth of high crystalline quality on the exfoliated surfaces for III-V photovoltaics. Also disclosed herein are methods for growing GaAs (111) on layered-2D Bi.sub.2Se.sub.3 (0001) substrates in an MOCVD reactor.

A new class of compounds known as chalcogenosilacyclopentanes is described. These compounds are five-membered ring structures containing a silicon-selenium or silicon-tellurium bond, as shown in Formulas (I) and (II). In these compounds, the substituents on the silicon and on the ring carbons may be hydrogen, alkyl, alkoxy, aromatic, or ether groups. The chalcogenosilacyclopentane compounds undergo ring-opening reactions with hydroxyl and other protic functionalities and may be used to prepare substrates that are amenable to thin film deposition techniques such as ALD and CVD.

##STR00001##

The present invention discloses a semiconductor structure and a method for manufacturing the semiconductor structure. The semiconductor structure includes: a substrate; and at least one composition adjusting layer disposed above the substrate; wherein each of the at least one composition adjusting layer is made of a semiconductor compound, the semiconductor compound at least comprises a first element and a second element, and an atomic number of the first element is less than an atomic number of the second element, wherein in each of the at least one composition adjusting layer, along an epitaxial direction of the substrate, an atomic percentage of the first element in a compound composition is gradually decreased at first and then gradually increased, a thickness of a gradual decrease section is greater than a thickness of a gradual increase section.

A photovoltaic device is presented. The photovoltaic device includes a layer stack; and an absorber layer is disposed on the layer stack. The absorber layer comprises selenium, wherein an atomic concentration of selenium varies across a thickness of the absorber layer. The photovoltaic device is substantially free of a cadmium sulfide layer.

A method includes forming a 2-D material semiconductor layer over a substrate; forming source/drain electrodes covering opposite sides of the 2-D material semiconductor layer, while leaving a portion of the 2-D material semiconductor layer exposed by the source/drain electrodes; forming a first gate dielectric layer over the portion of the 2-D material semiconductor layer by using a physical deposition process; forming a second gate dielectric layer over the first gate dielectric layer by using a chemical deposition process, in which a thickness of the first gate dielectric layer is less than a thickness of the second gate dielectric layer; and forming a gate electrode over the second gate dielectric layer.

The invention provides a semiconductor structure and a method of preparing a semiconductor structure, which solves the problems of easy cracking, large warpage and large dislocation density which exist in a semiconductor compound epitaxial structure epitaxially grown on a substrate in the prior art. The semiconductor structure includes: a substrate; at least one periodic structure disposed over the substrate; wherein each of the periodic structures includes at least one period, each period including a first periodic layer and a second periodic layer which are sequentially stacked in an epitaxial direction.

A method of making a photovoltaic cell includes providing a metal oxide substrate. The substrate is at least translucent to light. The substrate is directed through a deposition chamber. A semiconductor is deposited over a first major surface of the substrate. The semiconductor includes a polycrystalline p-type layer. The semiconductor is exposed to a chlorine-containing compound or a chlorine molecule. A second electrode layer is provided over the semiconductor.

A photovoltaic device is presented. The photovoltaic device includes a layer stack; and an absorber layer is disposed on the layer stack. The absorber layer comprises selenium, wherein an atomic concentration of selenium varies across a thickness of the absorber layer. The photovoltaic device is substantially free of a cadmium sulfide layer.

The invention provides a semiconductor structure and a method of preparing a semiconductor structure, which solves the problems of easy cracking, large warpage and large dislocation density which exist in a semiconductor compound epitaxial structure epitaxially grown on a substrate in the prior art. The semiconductor structure includes: a substrate; at least one periodic structure disposed over the substrate; wherein each of the periodic structures includes at least one period, each period including a first periodic layer and a second periodic layer which are sequentially stacked in an epitaxial direction.