An intermediate substrate includes a handle substrate bonded to a thin layer suitable for epitaxial growth of a compound semiconductor layer, such as a III-nitride semiconductor layer. The handle substrate may be a metal or metal alloy substrate, such as a molybdenum or molybdenum alloy substrate, while the thin layer may be a sapphire layer. A method of making the intermediate substrate includes forming a weak interface in the source substrate, bonding the source substrate to the handle substrate, and exfoliating the thin layer from the source substrate such that the thin layer remains bonded to the handle substrate.

Bonded intermediate substrate and method of making same

In one embodiment, a method of forming a multijunction solar cell having lattice mismatched layers and lattice-matched layers comprises growing a top subcell having a first band gap over a growth semiconductor substrate. A middle subcell having a second band gap is grown over the top subcell, and a lower subcell having a third band gap is grown over the middle subcell. The lower subcell is substantially lattice-mismatched with respect to the growth semiconductor substrate. The first band gap of the top subcell is larger than the second band gap of the middle subcell. The second band gap of the middle subcell is larger than the third band gap of the lower subcell. A support substrate is formed over the lower subcell, and the growth semiconductor substrate is removed. In various embodiments, the multijunction solar cell may further comprise additional lower subcells. A parting layer may also be provided between the growth substrate and the top subcell in certain embodiments. Embodiments of this reverse process permit the top and middle subcells to have high performance by having atomic lattice spacing closely matched to that of the growth substrate. Lower subcells can be included with appropriate band gap, but with lattice spacing mismatched to the other subcells. The reduced performance caused by strain resulting from mismatch can be mitigated without reducing the performance of the upper subcells.

High efficiency, monolithic multijunction solar cells containing lattice-mismatched materials and methods of forming same

III-V semiconductors, GaAs and in particular InGaP, are used in many different electronic applications, such as high power and high frequency devices, laser diodes and high brightness LED. Their direct bandgap and high reliability make them ideal candidates for the realisation of high efficiency solar cells: in the past years they have been successfully used as power sources for satellites in space, where they are able to produce electricity from sunlight with an overall efficiency of around 30%. Nowadays, the use of arsenides and phosphides as photovoltaic (PV) devices is confined only to space applications since their price is much higher than conventional Si flat panel modules, the leading PV market technology. But with the introduction of multijunction solar cells capable of operating in high concentration solar light, the area and, therefore, the cost of these cells can be reduced and will eventually find an application and market also on Earth. This article will review the situation of semiconductor solar cell materials, focusing on Si, GaAs, InGaP and multijunction solar cells and will discuss future trends and possibilities of bringing III-V technology from space to Earth. Copyright © 2006 John Wiley & Sons, Ltd.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/pip.715

The potential of III-V semiconductors as terrestrial photovoltaic devices

A multi-junction solar cell includes a silicon solar subcell, a GaInP solar subcell, and a GaAs solar subcell located between the silicon solar subcell and the GaInP solar subcell. The GaAs solar subcell is bonded to the silicon solar subcell such that a bonded interface exists between these subcells.

GaInP/GaAs/Si TRIPLE JUNCTION SOLAR CELL ENABLED BY WAFER BONDING AND LAYER TRANSFER

A solar cell module includes: two solar cells, each including an photoelectric conversion body 10a, 10b having first and second main faces and generating photogenerated carriers, a first electrode provided on the first main face, and a second electrode provided on the first or second main face and having a polarity opposite to that of the first electrode; and a wiring member 2a for electrically connecting the first electrode of one of the two solar cells to the second electrode of the other solar cell. The first electrode has a plurality of finger electrodes for collecting the photogenerated carriers generated in the photoelectric conversion body 10a and a bus-bar electrode 11a for collecting the photogenerated carriers collected by the plurality of finger electrodes. The wiring member 2a is connected onto the bus-bar electrode 11a of the one solar cell through a connection layer 13 formed of a conductive resin containing conductive material. The connection layer 13 is also in contact with the first main face of the photoelectric conversion body 10a.

Solar cell module

A solar cell comprises a crystalline substrate having projections and depressions formed on either side or both sides of the substrate, wherein a projection-depression depth is 25 μm or more.

Solar cell and production process therefor

The object of the invention is to provide a solar panel and a method for manufacturing the same, wherein the manufacture of the solar panel for use in space and repair work thereon can be performed easily and in little time. An entirety of the solar panel is configured by detachably linking a plurality of unit solar cell modules, which include a plurality of solar cells and connection wires for connecting the solar cells, and electrically connecting the unit solar cell modules to one another. Thus, a solar panel can be easily fabricated by combining standardized unit solar cell modules. Moreover, by simply mechanically connecting the unit solar cell modules, they can be electrically connected, and thus the time necessary for manufacture or repair of solar panels can be shortened.

Solar panel for space and method for manufacturing the same

A photoelectric converting device is provided with enhanced photoelectric conversion efficiency by optimizing a combination of materials used for top and bottom cells. The photoelectric converting device of the present invention is provided with first and second pn junctions. The first pn junction is formed in a semiconductor substantially represented by (Al 1−y Ga y ) 1−x In x P, and the second pn junction is formed in a semiconductor substantially represented by Ga 1−z In z As.

Photoelectric converting device

Although technologies for the InGaP/InGaAs/Ge cell have been matured, there is still room for improvement of the InGaP/(In)GaAs/Ge cell in practical level. Band gap of the top cell should be increased a little to get higher V/sub OC/. Thinning the Ge substrate is thought to be effective to increase a power per weight even for rigid panel. For concentrator application, grid pitch, cell size and current matching design should be optimized with taking account of the spectrum of concentrated light. The InGaP/(In)GaAs based solar cells shall be cornerstone in high efficiency multijunction solar cells in future. High efficiency cell consisted of 1 eV lattice-match material such as InGaAsN is strongly desired for high efficiency 4-junction or 6-junction cell. Wafer bonding and layer transfer techniques might be sophisticated to make solar cells. Paper-like InGaP/GaAs solar cells with efficiency of 29.4% on flexible metal film developed by SHARP Corp. are newly reported. Material cost of the cell is basically very low, because it has only very thin layers of III-V compounds and cheap metal film. Thin film technology shall be a hint for future cells.

Future development of InGaP/(In)GaAs based multijunction solar cells

A process for producing a solar cell comprises the steps of; forming at least one electrode on a first surface of a semiconductor substrate for constructing a solar cell, attaching a support substrate to the first surface of the semiconductor substrate on which said electrode is formed, and then processing the semiconductor substrate into a thin-film semiconductor substrate.

Kazuyo Nakamura

Papers

Solar cell and production process therefor

Solar panel for space and method for manufacturing the same

Photoelectric converting device

Future development of InGaP/(In)GaAs based multijunction solar cells

Process for producing solar cells and solar cells produced thereby