Abstract: Methods for fabrication of copper delafossite materials include a low temperature sol-gel process for synthesizing CuBO2 powders, and a pulsed laser deposition (PLD) process for forming thin films of CuBO2, using targets made of the CuBO2 powders. The CuBO2 thin films are optically transparent p-type semiconductor oxide thin films. Devices with CuBO2 thin films include p-type transparent thin film transistors (TTFT) comprising thin film CuBO2, as a channel layer and thin film solar cells with CuBO2 p-layers. Solid state dye sensitized solar cells (SS-DSSC) comprising CuBO2 in various forms, including “core-shell” and “nano-couple” particles, and methods of manufacture, are also described.

Abstract: An electrode for photoelectric conversion elements having high initial characteristics and excellent durability, a manufacturing method of the electrode for photoelectric conversion elements, and a dye-sensitized solar cell are provided. An electrode for photoelectric conversion elements according to the present invention has a structure in which a metal oxide layer containing zinc oxide is provided on a base. The metal oxide layer has a plurality of bump-like protrusions formed so as to protrude radially from the base side, and also has an emission peak in a region of 350 to 400 nm in cathodoluminescence measurement. The metal oxide layer is preferably heat treated at 220 to 500° C.

Abstract: A method for fabricating a photovoltaic element with stabilised efficiency is proposed. The method comprises the following steps: preparing a boron-doped, oxygen-containing silicon substrate; forming an emitter layer on a surface of the silicon substrate; and a stabilisation treatment step. The stabilisation treatment step comprises keeping the temperature of the substrate during a treatment time within a selectable temperature range having a lower temperature limit of 50° C., preferably 90° C., more preferably 130° C. and even more preferably 160° C. and an upper temperature limit of 230° C., preferably 210° C., more preferably 190° C. and even more preferably 180° C., and generating excess minority carriers in the silicon substrate during the treatment time, for example, by illuminating the substrate or by applying an external voltage. This method can be used to fabricate a photovoltaic element, e.g.

Abstract: A solar cell is provided as one capable of increasing the open voltage when compared with the conventional solar cells. A solar cell according to the present invention has a p-type semiconductor layer containing a group Ib element, a group IIIb element, and a group VIb element, and an n-type semiconductor layer containing a group Ib element, a group IIIb element, a group VIb element, and Zn and formed on the p-type semiconductor layer. A content of the group Ib element in the n-type semiconductor layer is from 15 to 21 at. % to the total number of atoms of the group Ib element, the group IIIb element, the group VIb element, and Zn in the n-type semiconductor layer, and a content of Zn in the n-type semiconductor layer is from 0.005 to 1.0 at. % to the total number of atoms of the group Ib element, the group IIIb element, the group VIb element, and Zn in the n-type semiconductor layer.

Abstract: A solar cell which can increase its open-circuit voltage, short-circuit current, and fill factor (F.F.), thereby enhancing its conversion efficiency is provided. The solar cell of the present invention comprises a p-type semiconductor layer and an n-type semiconductor layer, formed on the p-type semiconductor layer, containing a compound expressed by the following chemical formula (1): ZnO1-x-ySxSey??(1) where x?0, y>0, and 0.2<x+y<0.65.

Abstract: A graphene-on-oxide substrate according to the present invention includes: a substrate having a metal oxide layer formed on its surface; and, formed on the metal oxide layer, a graphene layer including at least one atomic layer of the graphene. The graphene layer is grown generally parallel to the surface of the metal oxide layer, and the inter-atomic-layer distance between the graphene atomic layer adjacent to the surface of the metal oxide layer and the surface atomic layer of the metal oxide layer is 0.34 nm or less. Preferably, the arithmetic mean surface roughness Ra of the metal oxide layer is 1 nm or less.

Abstract: A method of forming an organic layer by using a liquid composition comprising a small molecule organic semiconductor material mixed in a ketone solvent. The liquid composition is deposited on a surface to form the organic layer. The ketone solvent may be an aromatic ketone solvent, such as a tetralone solvent. The organic semiconductor material may be cross-linkable to provide a cross-linked organic layer. The method can be used to make organic electronic devices, such as organic light emitting devices. In another aspect, the liquid composition comprises a small molecule organic semiconductor material mixed in an aromatic ether solvent. Also, provided are liquid compositions which can be used to make organic layers.

Abstract: In general, the present invention relates to forming electrical contacts in a semiconductor device, including contact regions in solar cells. According to certain aspects, the invention provides methods and apparatuses for forming plated contacts in the presence of a thin tunnel oxide. Preferably, the tunnel oxide dielectric layer is thin enough to sustain a tunnel current. Plating over the tunnel dielectric is then performed. The benefits of the invention include that no annealing is required to form the metal-silicide contact. Moreover, there is no requirement for special metals for n- or p-type contacts. Another advantage is that shallow contacts according to the invention avoid punching through a shallow junction, thereby enabling the use of shallower emitters with improved blue response. Still further, there is no need to control the amount of silicide metal plated in order to prevent driving the silicide alloy through the junction.

Abstract: The present application utilizes an oxidation process to fabricating a Group III-V compound semiconductor solar cell device. By the oxidation process, a window layer disposed on a cell unit is oxidized to enhance the efficiency of the solar cell device. The oxidized window has an increased band gap to minimize the surface recombination of electrons and holes. The oxidized window also improves transparency at the wavelengths that were absorbed in the conventional window layer.

Abstract: A photoelectric conversion device comprising a lower electrode, an upper electrode opposing to the lower electrode and a photoelectric conversion layer provided between the lower electrode and the upper electrode, the photoelectric conversion device being for collecting a photocurrent upon application of a bias voltage between the lower electrode and the upper electrode, wherein the upper electrode works as an electrode in a light incident side, the upper electrode is transparent, and the lower electrode is a metallic electrode having a function to reflect light.

Abstract: A back contact integrated photovoltaic cell includes a substrate having a dielectric surface and a patterned metal layer with parallel spaced alternately positive and negative electrode fingers forming an interdigitated two-terminal structure over the dielectric surface of the substrate. A dielectric filler may be in the interstices of separation between adjacent spaced parts of the patterned metal layer. Parallel spaced strips, alternately of p+ doped polysilicon and of n+ doped polysilicon, may top the positive and negative interdigitated electrode fingers, respectively, and form doped p-type active regions and n-type active regions of the integrated photovoltaic cell, spaced and isolated by a strip of undoped or negligibly doped polysilicon. An n? or p? doped or intrinsic semiconducting layer of at least partly crystallized silicon, forming a semiconductor region of thickness adapted to maximize absorption of photonic energy when illuminated by sunlight, may cover the interdigitated active doped regions.

Abstract: The present invention provides a method of manufacturing a crystalline silicon solar cell, comprising: —providing a crystalline silicon substrate having a front side and a back side; —forming a thin silicon oxide film on at least one of the front and the back side by soaking the crystalline silicon substrate in a chemical solution; —forming a dielectric coating film on the thin silicon oxide film on at least one of the front and the back side. The thin silicon oxide film may be formed with a thickness of 0.5-10 nm. By forming a oxide layer using a chemical solution, it is possible to form a thin oxide film for surface passivation wherein the relatively low temperature avoids deterioration of the semiconductor layers.

Abstract: A multijunction solar cell including an upper first solar subcell having a first band gap; a middle second solar subcell adjacent to the first solar subcell and having a second band gap smaller than the first band gap, and having a base layer and an emitter layer, a graded interlayer adjacent to the second solar subcell; the graded interlayer having a third band gap greater than said second band gap; a third solar subcell adjacent to the interlayer, the third subcell having a fourth band gap smaller than the second band gap such that the third subcell is lattice mismatched with respect to the second subcell; and a distributed Bragg reflector (DBR) adjacent the second or third subcell.

Abstract: There is provided a semiconductor substrate for solid-state image sensing device in which the production cost is lower than that of a gettering method through a carbon ion implantation and problems such as occurrence of particles at a device production step and the like are solved. Silicon substrate contains solid-soluted carbon having a concentration of 1×1016-1×1017 atoms/cm3 and solid-soluted oxygen having a concentration of 1.4×1018-1.6×1018 atoms/cm3.

Abstract: The present disclosure is directed to a method for automated manufacturing thin film solar cells including a laser processed layer. The method includes depositing a plurality of substantially planar layers in proximity with one another, including at least a first semiconductor layer, feeding the plurality of layers through a plurality of processing steps, irradiating at least a portion of a layer of the plurality of layers with a source of laser radiation, and using a control computer to control at least one of the acts of feeding and irradiating in the automated manufacture of the thin film solar cells.

Abstract: The present invention provides materials, devices, and methods for generation of electricity from solar power. In one aspect, the present invention includes a solar cell, including a first conductor, a doped silicon layer in electrical communication with the first conductor, a nanodiamond layer in contact with the doped silicon layer, a doped amorphous diamond layer in contact with the nanodiamond layer, and a second conductor in electrical communication with the doped amorphous diamond layer.

Abstract: A present method of manufacturing a silicon-based thin-film photoelectric conversion device is characterized in that a double pin structure stack body is formed by successively forming, in an identical plasma CVD film deposition chamber, a first p-type semiconductor layer, an i-type amorphous silicon-based photoelectric conversion layer, a first n-type semiconductor layer, a second p-type semiconductor layer, an i-type microcrystalline silicon-based photoelectric conversion layer, and a second n-type semiconductor layer on a transparent conductive film formed on a substrate, and the first p-type semiconductor layer, the i-type amorphous silicon-based photoelectric conversion layer and the first n-type semiconductor layer are formed under such conditions that a film deposition pressure in the plasma CVD film deposition chamber is not lower than 200 Pa and not higher than 3000 Pa and power density per unit electrode area is not lower than 0.01 W/cm2 and not higher than 0.3 W/cm2.

Abstract: A highly-efficient photoelectric conversion device is provided without complicating the manufacturing process. The photoelectric conversion device includes a unit cell having a semiconductor junction, in which a first impurity semiconductor layer having one conductivity type, a semiconductor layer including a first semiconductor region having a larger proportion of a crystalline semiconductor than an amorphous semiconductor and a second semiconductor region having a larger proportion of an amorphous semiconductor than a crystalline semiconductor and including both a radial crystal and a crystal having a needle-like growing end in the amorphous semiconductor, and a second impurity semiconductor layer having a conductivity type opposite to the conductivity type of the first impurity semiconductor layer are stacked in this order.

Abstract: The present invention provides a photoelectric conversion element having a high power generation efficiency, raising no problem of corrosion, and being applicable to a substrate having a low heat resistance, as well as a method of producing the same. Two sheets of photocatalyst electrodes (10) constructed by forming a photocatalyst film (8) dyed with a photosensitizing dye on one surface of a transparent substrate (1) via a transparent conductive film (2) are disposed to oppose each other. A counter electrode (11) is disposed between these electrodes. The counter electrode is constructed in such a manner that, via a conductive adhesive agent layer (7) that covers the whole of the non-opening parts on both surfaces of a counter electrode substrate (4) having a plurality of openings (9), a brush-shaped carbon nanotube (5) that is oriented substantially perpendicularly to the substrate surface is disposed.

Abstract: To improve a transmission rate of an antireflection film, the antireflection film includes: a first silicon oxide film (2), which is formed on a silicon substrate (1); a polysilicon film (3), which is formed on the first silicon oxide film (2) to a thickness of 6 nm through 14 nm; and a second silicon oxide film (4), which is formed on the polysilicon film (3). The transmission rate of the antireflection film is further improved if a thickness of the first silicon oxide film (2) is set to 14 nm through 35 nm. When used in a photoelectric conversion element for such as a solid state image sensor and a photovoltaic generator, the antireflection film may enhance efficiency of photoelectric conversion.

Abstract: Described herein is a tile made up of: a ceramic base body having an absorption of water equal to or less than 0.5 wt %; a photovoltaic cell applied directly to a first surface of the ceramic base body; a device containing the electrical and/or electronic part, applied to a second surface of the ceramic base body; and an electrical connector, designed to connect the photovoltaic cell electrically to the device containing the electrical and/or electronic part through the ceramic base body.

Abstract: A design and manufacturing method for an interdigitated backside contact photovoltaic (PV) solar cell less than 100 ?m thick are disclosed. A porous silicon layer is formed on a wafer substrate. Portions of the PV cell are then formed using diffusion, epitaxy and autodoping from the substrate. All backside processing of the solar cell (junctions, passivation layer, metal contacts to the N+ and P+ regions) is performed while the thin epitaxial layer is attached to the porous layer and substrate. After backside processing, the wafer is clamped and exfoliated. The front of the PV cell is completed from the region of the wafer near the exfoliation fracture layer, with subsequent removal of the porous layer, texturing, passivation and deposition of an antireflective coating. During manufacturing, the cell is always supported by either the bulk wafer or a wafer chuck, with no processing of bare thin PV cells.

Abstract: A material for forming a conductive structure for a micromechanical current-driven device is described, which is an alloy containing about 0.025% manganese and the remainder nickel. Data shows that the alloy possesses advantageous mechanical and electrical properties. In particular, the sheet resistance of the alloy is actually lower and more stable than the sheet resistance of the pure metal. Accordingly, when used for conductive leads in a photonic device, the leads using the NiMn alloy may provide current to heat the photonic device while generating less heat within the leads themselves, and a more stable output.

Abstract: A solar cell is provided in which an amorphous semiconductor layer (15) is located on a back surface of a crystalline silicon structure to form a heterojunction. A first contact structure contacts the crystalline layer (14) and a second contact structure contacts the amorphous layer (15). A method of forming the heterojunction solar cell is also provided in which a doped amorphous semiconductor layer (15) is formed on an oppositely doped crystalline silicon layer (14), to form a rear surface heterojunction with the crystalline silicon layer (14). Subsequently a rear surface contact (16) is formed, to contact to the amorphous semiconductor layer (15), and a heavily doped region (13) of the same conductivity type as the crystalline silicon layer (14) is formed in contact with the crystalline silicon layer (14) wherever metal contacts (10) are required contact the crystalline silicon layer (14) to facilitate contact with the subsequently formed metal contact (10).

Abstract: An antireflective coating for silicon-based solar cells comprising amorphous silicon carbonitride, wherein the amount of carbon in the silicon carbonitride is from 5 to 25%, a solar cell comprising the antireflective coating, and a method of preparing the antireflective coating.

Abstract: The present invention provides an optoelectronic memory device, the method for manufacturing and evaluating the same. The optoelectronic memory device according to the present invention includes a substrate, an insulation layer, an active layer, source electrode and drain electrode. The substrate includes a gate, and the insulation layer is formed on the substrate. The active layer is formed on the insulation layer, and more particularly, the active layer is formed of a composite material comprising conjugated conductive polymers and quantum dots. Moreover, both of the source and the drain are formed on the insulation layer, and electrically connected to the active layer.

Abstract: A light emitting element has a substrate of gallium oxides and a pn-junction formed on the substrate. The substrate is of gallium oxides represented by: (AlxInyGa(1?X?Y))2O3 where 0?x?1, 0?y?1 and 0?x+y?1. The pn-junction has first conductivity type substrate, and GaN system compound semiconductor thin film of second conductivity type opposite to the first conductivity type.

Abstract: An optical semiconductor device includes a lower electrode layer formed over a semiconductor substrate, an infrared absorption layer formed over the lower electrode layer 26, and an upper electrode layer 38 formed over the infrared absorption layer 36. The infrared absorption layer includes a quantum dot having dimensions different among directions stacked, and is sensitive to infrared radiation of wavelengths different corresponding to polarization directions.

Abstract: A method for fabricating an image sensor is provided. In the image sensor fabrication method, an interconnection and a dielectric interlayer are formed on a semiconductor substrate including a readout circuit. An image sensing unit is formed on a carrier substrate of one side of a dielectric layer. The carrier substrate and the dielectric interlayer are bonded to each other. The dielectric layer and the carrier substrate are removed to leave the image sensing unit on the dielectric interlayer.

Abstract: In various embodiments, fiber photovoltaic devices are described in the present disclosure. The fiber photovoltaic devices include an optical filament, a first electrode coating the optical filament, a continuous semiconductive layer deposited above the first electrode layer, and a second electrode layer deposited above the continuous semiconductive layer. The first electrode layer is at least partially transparent to electromagnetic radiation. The continuous semiconductive layer is in electrical contact with the first electrode layer. The continuous semiconductive layer absorbs electromagnetic radiation and turns the electromagnetic radiation into an electrical signal. The continuous semiconductive layer includes at least two semiconductive materials that are substantially unmixed and are located in separate regions along the longitudinal axis of the fiber photovoltaic device. The second electrode layer is in electrical contact with the continuous semiconductive layer.

Abstract: A thin film transistor (TFT) using an oxide semiconductor as an active layer, a method of manufacturing the TFT, and a flat panel display device having the TFT include a gate electrode formed on a substrate; an active layer made of an oxide semiconductor and insulated from the gate electrode by a gate insulating layer; source and drain electrodes coupled to the active layer; and an interfacial stability layer formed on one or both surfaces of the active layer. In the TFT, the interfacial stability layer is formed of an oxide having a band gap of 3.0 to 8.0 eV. Since the interfacial stability layer has the same characteristic as a gate insulating layer and a passivation layer, chemically high interface stability is maintained. Since the interfacial stability layer has a band gap equal to or greater than that of the active layer, charge trapping is physically prevented.

Abstract: Described herein is an optically controlled electrical-switch device which includes a first current-conduction terminal and a second current-conduction terminal, and a carbon nanotube connected between the first and the second current-conduction terminals, the carbon nanotube being designed to be impinged upon by electromagnetic radiation and having an electrical conductivity that can be varied by varying the polarization of the electromagnetic radiation incident thereon. In particular, the carbon nanotube may for example, in given conditions of electrical biasing, present a high electrical conductivity when it is impinged upon by electromagnetic radiation having a given wavelength and a polarization substantially parallel to the axis of the carbon nanotube itself, and a reduced electrical conductivity when it is impinged upon by electromagnetic radiation having a given wavelength and a polarization substantially orthogonal to the axis of the carbon nanotube itself.

Abstract: Optical and optoelectronic devices and methods of making same. Under one aspect, an optical device includes an integrated circuit an array of conductive regions; and an optically sensitive material over at least a portion of the integrated circuit and in electrical communication with at least one conductive region of the array of conductive regions. Under another aspect, a method of forming a nanocrystalline film includes fabricating a plurality of nanocrystals having a plurality of first ligands attached to their outer surfaces; exchanging the first ligands for second ligands of different chemical composition than the first ligands; forming a film of the ligand-exchanged nanocrystals; removing the second ligands; and fusing the cores of adjacent nanocrystals in the film to form an electrical network of fused nanocrystals.

Abstract: A photoelectric conversion device and a method for manufacturing the same are provided. The photoelectric conversion device includes a first semiconductor layer including a first impurity element over a substrate, a second semiconductor layer including an amorphous layer and a crystal over the first semiconductor layer, and a third semiconductor layer including a second impurity element over the second semiconductor layer. The crystal penetrates between the first semiconductor layer and the third semiconductor layer.

Abstract: An interferometric mask covering the front electrodes of a photovoltaic device is disclosed. Such an interferometric mask may reduce reflections of incident light from the electrodes. In various embodiments, the mask reduces reflections so that a front electrode pattern appears similar in color to adjacent regions of visible photovoltaic active material.

Abstract: Provided is an image sensor using a photo-detecting molecule and a method of operating the image sensor. The image sensor may include a plurality of first electrodes disposed parallel to each other and a plurality of second electrodes disposed parallel to each other in a direction perpendicular to the first electrodes and above the first electrodes, and a plurality of subpixels formed in regions where the first electrodes cross the second electrodes. Each of the subpixels may comprise a photo-detecting molecule layer that may generate charges by absorbing light having a certain wavelength, a charge generation layer that may form a plurality of secondary electrons by receiving the charges from the photo-detecting molecule layer when a known voltage is applied between the first electrodes and the second electrodes, and a variable resistance layer, an electrical state of which is changed by receiving the secondary electrons generated from the charge generation layer.

Abstract: Example embodiments provide a non-linear solar cell module. The non-linear solar cell module may include a plurality of photovoltaic cells. Each of the photovoltaic cells may comprise a lower electrode on a substrate, a photovoltaic conversion layer on the lower electrode, and an upper electrode formed on the photovoltaic conversion layer, and the photovoltaic cells may be in a non-linear shape.

Abstract: Solar cell modules are provided having a solar cell layer and a colored multi-layer encapsulant sheet where an uncolored surface sub-layer of the encapsulant sheet is in direct contact with the solar cell layer.

Abstract: Solar cells include a substrate having a light collecting surface thereon and a P-N rectifying junction within the substrate. The P-N rectifying junction includes a base region of first conductivity type (e.g., p-type) and a semiconductor layer of second conductivity type extending between the base region and the light collecting surface. A trench is also provided, which extends through the semiconductor layer and into the base region. First and second electrodes are provided adjacent the light collecting surface. The first electrode is electrically coupled to the semiconductor layer and the second electrode is electrically coupled to the base region, at a location adjacent a bottom of the trench.

Abstract: Electrical devices comprised of nanowires are described, along with methods of their manufacture and use. The nanowires can be nanotubes and nanowires. The surface of the nanowires may be selectively functionalized. Nanodetector devices are described.

Abstract: An optical waveguide includes a silicon wafer having two opposed sides. A first notch is defined in each of the two opposed sides such that the silicon wafer includes a head portion and a first stem portion.

Abstract: An image sensor pixel includes a substrate, an epitaxial layer, and a light collection region. The substrate is doped to have a first conductivity type. The epitaxial layer is disposed over the substrate and doped to have a second conductivity type opposite of the first conductivity type. The light collection region is disposed within the epitaxial layer for collecting photo-generated charge carriers. The light collection region is doped to have the first conductivity type as well.

Abstract: Embodiments of the invention relate to a silicon semiconductor device, and a conductive paste for use in the front side of a solar cell device.

Abstract: The present invention includes a template, an optoelectronic device and methods for making the same. The optoelectronic device includes a first substrate; a first electrode disposed on the first substrate; a first interdigitating, nano-structured charge-transfer molded material (e.g., a polymer) with a first electron affinity disposed on the first electrode; a second interdigitating, nano-structured charge-transfer material (e.g., single molecules, quantum dots, or particles) with a second electron affinity disposed on the first interdigitating, nano-structured charge-transfer material; a second electrode disposed in the second interdigitating, nano-structured charge-transfer material; and a second substrate disposed on the second electrode.

Abstract: A photo-detector with a reduced G-R noise comprises two n-type narrow bandgap layers surrounding a middle barrier layer having an energy bandgap at least equal to the sum of the bandgaps of the two narrow bandgap layers. Under the flat band conditions the conduction band edge of each narrow bandgap layer lies below the conduction band edge of the barrier layer by at least the bandgap energy of the other narrow bandgap layer. When biased with an externally applied voltage, the more negatively biased narrow bandgap layer is the contact layer and the more positively biased narrow bandgap layer is the photon absorbing layer.

Abstract: Provided are a newly developed dye-sensitizing type photoelectric conversion element employing a highly durable sensitizing dye, exhibiting high photoelectric conversion efficiency, and a solar cell fitted with the photoelectric conversion element. Also disclosed is a photoelectric conversion element comprising a compound represented by Formula (1) between a pair of facing electrodes.

Abstract: The present invention discloses thin film photovoltaic devices comprising Group II-VI semiconductor layers with a substrate configuration having an interface layer between the absorber layer and the window layer to create improved junctions. The present invention also discloses methods for making and surface treatments for thin film photovoltaic devices comprising Group II-VI semiconductor layers with a substrate configuration to create devices with improved junctions.

Abstract: A method for producing photoactive layers, and components, such as solar cells, including the layers. According to the invention, the photoactive layers are produced by forming a non-semiconducting layer from precursor material including at least one metal compound and a salt-like and/or organic reactant on a substrate by printing or blade coating, the layer being exposed to temperatures of less than 300° C., wherein a semiconducting, photoactive layer is formed from the non-semiconducting layer by thermal conversion of the precursor material.

Abstract: A translucent solar cell has a transparent substrate and a first translucent electrode that is in anode. A transparent active layer, that is a substantially organic material layer, is formed on top of the anode. On top of the active layer, a second translucent electrode is formed. The second translucent electrode is the cathode. In a variation, the first translucent electrode is the cathode and the second translucent electrode the anode. The flexibility in choosing the order of the anode and cathode relative to the transparent substrate allows for an increase in processing techniques and, thus, the amount of utilizable materials to increase the power conversion efficiency of translucent solar cells.

Abstract: Modeling a monolithic, multi-bandgap, tandem, solar photovoltaic converter or thermophotovoltaic converter by constraining the bandgap value for the bottom subcell to no less than a particular value produces an optimum combination of subcell bandgaps that provide theoretical energy conversion efficiencies nearly as good as unconstrained maximum theoretical conversion efficiency models, but which are more conducive to actual fabrication to achieve such conversion efficiencies than unconstrained model optimum bandgap combinations. Achieving such constrained or unconstrained optimum bandgap combinations includes growth of a graded layer transition from larger lattice constant on the parent substrate to a smaller lattice constant to accommodate higher bandgap upper subcells and at least one graded layer that transitions back to a larger lattice constant to accommodate lower bandgap lower subcells and to counter-strain the epistructure to mitigate epistructure bowing.