Abstract: Photon absorption, and thus current generation, is hindered in conventional thin-film solar cell designs, including quantum well structures, by the limited path length of incident light passing vertically through the device. Optical scattering into lateral waveguide structures provides a physical mechanism to increase photocurrent generation through in-plane light trapping. However, the insertion of wells of high refractive index material with lower energy gap into the device structure often results in lower voltage operation, and hence lower photovoltaic power conversion efficiency. The voltage output of an InGaAs quantum well waveguide photovoltaic device can be increased by employing a III-V material structure with an extended wide band gap emitter heterojunction.

Abstract: Material and antireflection structure designs and methods of manufacturing are provided that produce efficient photovoltaic power conversion from single- and multijunction devices. Materials of different energy gap are combined in the depletion region of at least one of the semiconductor junctions. Higher energy gap layers are positioned to reduce the diode dark current and enhance the operating voltage by suppressing both carrier injections across the junction and recombination rates within the junction. Step-graded antireflection structures are placed above the active region of the device in order to increase the photocurrent.

Abstract: A new solar cell structure called a heterojunction barrier solar cell is described. As with previously reported quantum-well and quantum-dot solar cell structures, a layer of narrow band-gap material, such as GaAs or indium-rich InGaP, is inserted into the depletion region of a wide band-gap PN junction. Rather than being thin, however, the layer of narrow band-gap material is about 400-430 nm wide and forms a single, ultrawide well in the depletion region. Thin (e.g., 20-50 nm), wide band-gap InGaP barrier layers in the depletion region reduce the diode dark current. Engineering the electric field and barrier profile of the absorber layer, barrier layer, and p-type layer of the PN junction maximizes photogenerated carrier escape. This new twist on nanostructured solar cell design allows the separate optimization of current and voltage to maximize conversion efficiency.

Abstract: A method for fabricating a solar cell commences by bonding a first metal-coated substrate to a second metal-coated substrate to provide a bonded substrate. The bonded substrate is then coated with a first precursor solution to provide a coated bonded substrate. Finally, the procedure de-bonds the coated bonded substrate to provide a first solar cell device and a second solar cell device. A system for fabricating the solar cell comprises a first precursor solution deposition system containing a first precursor solution for deposition on a substrate, a first heating element for heating the substrate after deposition of the first precursor solution, a second precursor solution deposition system containing a second precursor solution for deposition on the substrate, and a second heating element for heating the substrate after deposition of the second precursor solution.

Abstract: Ultra-high reflectivity is projected for internal reflectors comprised of a metal film and nanostructured transparent conductive oxide (TCO) bi-layer on the back side of a semiconductor device. Oblique-angle deposition can be used to fabricate indium tin oxide (ITO) and other TCO optical thin-film coatings with a porous, columnar nanostructure. The resulting low-n dielectric films can then be employed as part of a conductive omni-directional reflector (ODR) structure capable of achieving high internal reflectivity over a broad spectrum of wavelengths and a wide range of angles. In addition, the dimensions and geometry of the nanostructured, low-n TCO films can be adjusted to enable diffuse reflections via Mie scattering. Diffuse ODR structures enhance the performance of light trapping and light guiding structures in photonic devices.

Abstract: Designs for ultra-high, broadband transmittance through windows over a wide range of incident angles are disclosed. The improvements in transmittance result from coating the windows with a new class of materials consisting of porous nanorods. A high transmittance optical window comprises a transparent substrate coated on one or both sides with a multiple layer coating. Each multiple layer coating includes optical films with a refractive index intermediate between the refractive index of the transparent substrate and air. The optical coatings are applied using an oblique-angle deposition material synthesis technique. The coating can be performed by depositing porous SiO2 layers using oblique angle deposition. The high transmittance window coated with the multiple layer coating exhibits reduced reflectance and improved transmittance, as compared to an uncoated transparent substrate.

Abstract: A bipolar transistor includes a base layer design and a method for fabricating such a bipolar transistor that employ a built-in accelerating field focused on a base region adjacent to a collector, where minority carrier transport is otherwise retarded. The accelerating field of the base layer includes on average, a relatively low p-doping level in a first region proximate to the collector and a relatively high p-doping level in a second region proximate to an emitter. Alternatively, the accelerating field can be derived from band gap grading, wherein the grade of band gap in the first region is greater than the grade of band gap in the second region, and the average band gap of the first region is lower than that of the second region.

Abstract: A new solar cell structure called a heterojunction barrier solar cell is described. As with previously reported quantum-well and quantum-dot solar cell structures, a layer of narrow band-gap material, such as GaAs or indium-rich InGaP, is inserted into the depletion region of a wide band-gap PN junction. Rather than being thin, however, the layer of narrow band-gap material is about 400-430 nm wide and forms a single, ultrawide well in the depletion region. Thin (e.g., 20-50 nm), wide band-gap InGaP barrier layers in the depletion region reduce the diode dark current. Engineering the electric field and barrier profile of the absorber layer, barrier layer, and p-type layer of the PN junction maximizes photogenerated carrier escape. This new twist on nanostructured solar cell design allows the separate optimization of current and voltage to maximize conversion efficiency.

Abstract: A solar cell device includes a p-n diode component over a substrate, the p-n diode component including at least one subcell, each subcell including an n-type semiconductor layer and a p-type semiconductor layer to form a p-n junction. The solar cell device further includes at least two features selected from: i) a nano-structured region between at the p-n junction of at least one subcell; ii) an n-type and/or a p-type layer of at least one subcell that includes a built-in quasi-electric field; and iii) a photon reflector structure. Alternatively, the solar cell device includes at least two subcells, and further includes a nano-structured region at the p-n junction of at least one of the subcells, wherein the subcells of the solar cell device are connected in parallel to each other by the p-type or the n-type semiconductor layer of each subcell.

Abstract: A bipolar transistor includes a base layer design and a method for fabricating such a bipolar transistor that employ a built-in accelerating field focused on a base region adjacent to a collector, where minority carrier transport is otherwise retarded. The accelerating field of the base layer includes on average, a relatively low p-doping level in a first region proximate to the collector and a relatively high p-doping level in a second region proximate to an emitter. Alternatively, the accelerating field can be derived from band gap grading, wherein the grade of band gap in the first region is greater than the grade of band gap in the second region, and the average band gap of the first region is lower than that of the second region.

Abstract: A bipolar transistor includes a base layer design and a method for fabricating such a bipolar transistor that employ a built-in accelerating field focused on a base region adjacent to a collector, where minority carrier transport is otherwise retarded. The accelerating field of the base layer includes on average, a relatively low p-doping level in a first region proximate to the collector and a relatively high p-doping level in a second region proximate to an emitter. Alternatively, the accelerating field can be derived from band gap grading, wherein the grade of band gap in the first region is greater than the grade of band gap in the second region, and the average band gap of the first region is lower than that of the second region.

Abstract: A photovoltaic (PV) device comprises at least one PV lamp that includes at least one solar cell chip that generates an electrical current upon exposure to light, and an epoxy lens that encapsulates the solar cell chip, the epoxy lens concentrating incident light onto the solar cell chip. A method of manufacturing a PV device that includes at least one PV lamp comprises fabricating at least one solar cell chip that generates an electrical current upon exposure to light, and forming an epoxy lens that encapsulates the solar cell chip, the epoxy lens concentrating incident light onto the solar cell chip, to thereby form the PV lamp.

Abstract: A semiconductor material which has a high carbon dopant concentration includes gallium, indium, arsenic and nitrogen. The disclosed semiconductor materials have a low sheet resistivity because of the high carbon dopant concentrations obtained. The material can be the base layer of gallium arsenide-based heterojunction bipolar transistors and can be lattice-matched to gallium arsenide emitter and/or collector layers by controlling concentrations of indium and nitrogen in the base layer. The base layer can have a graded band gap that is formed by changing the flow rates during deposition of III and V additive elements employed to reduce band gap relative to different III-V elements that represent the bulk of the layer. The flow rates of the III and V additive elements maintain an essentially constant doping-mobility product value during deposition and can be regulated to obtain pre-selected base-emitter voltages at junctions within a resulting transistor.

Abstract: A semiconductor material which has a high carbon dopant concentration and is composed of gallium, indium, arsenic and nitrogen is disclosed. The material is useful in forming the base layer of gallium arsenide based heterojunction bipolar transistors because it can be lattice matched to gallium arsenide by controlling the concentration of indium and nitrogen. The disclosed semiconductor materials have a low sheet resistivity because of the high carbon dopant concentration obtained.

Abstract: A semiconductor material which has a high carbon dopant concentration includes gallium, indium, arsenic and nitrogen. The disclosed semiconductor materials have a low sheet resistivity because of the high carbon dopant concentrations obtained. The material can be the base layer of gallium arsenide-based heterojunction bipolar transistors and can be lattice-matched to gallium arsenide emitter and/or collector layers by controlling concentrations of indium and nitrogen in the base layer. The base layer can have a graded band gap that is formed by changing the flow rates during deposition of III and V additive elements employed to reduce band gap relative to different III–V elements that represent the bulk of the layer. The flow rates of the III and V additive elements maintain an essentially constant doping-mobility product value during deposition and can be regulated to obtain pre-selected base-emitter voltages at junctions within a resulting transistor.

Abstract: A semiconductor material which has a high carbon dopant concentration includes gallium, indium, arsenic and nitrogen. The disclosed semiconductor materials have a low sheet resistivity because of the high carbon dopant concentrations obtained. The material can be the base layer of gallium arsenide-based heterojunction bipolar transistors and can be lattice-matched to gallium arsenide emitter and/or collector layers by controlling concentrations of indium and nitrogen in the base layer. The base layer can have a graded band gap that is formed by changing the flow rates during deposition of III and V additive elements employed to reduce band gap relative to different III-V elements that represent the bulk of the layer. The flow rates of the III and V additive elements maintain an essentially constant doping-mobility product value during deposition and can be regulated to obtain pre-selected base-emitter voltages at junctions within a resulting transistor.

Abstract: InP heterojunction bipolar transistors having a base layer of InGaAs which are compositionally graded to engineer the bandgap of the base layer to be larger at the emitter/base junction than at the collector/base junction. The graded bandgap can increase DC current gain and speed of the device. A metalorganic chemical vapor deposition method of preparing InP heterojunction bipolar transistors having a base layer with a relatively high concentration of carbon dopant. The high carbon dopant concentration lowers the base sheet resistivity and turn-on voltage of the device.

Abstract: A semiconductor material which has a high carbon dopant concentration and is composed of gallium, indium, arsenic and nitrogen is disclosed. The material is useful in forming the base layer of gallium arsenide based heterojunction bipolar transistors because it can be lattice matched to gallium arsenide by controlling the concentration of indium and nitrogen. The disclosed semiconductor materials have a low sheet resistivity because of the high carbon dopant concentration obtained.

Abstract: A semiconductor material which has a high carbon dopant concentration includes gallium, indium, arsenic and nitrogen. The disclosed semiconductor materials have a low sheet resistivity because of the high carbon dopant concentrations obtained. The material can be the base layer of gallium arsenide-based heterojunction bipolar transistors and can be lattice-matched to gallium arsenide emitter and/or collector layers by controlling concentrations of indium and nitrogen in the base layer. The base layer can have a graded band gap that is formed by changing the flow rates during deposition of III and V additive elements employed to reduce band gap relative to different III-V elements that represent the bulk of the layer. The flow rates of the III and V additive elements maintain an essentially constant doping-mobility product value during deposition and can be regulated to obtain pre-selected base-emitter voltages at junctions within a resulting transistor.

Abstract: InP heterojunction bipolar transistors having a base layer of InGaAs which are compositionally graded to engineer the bandgap of the base layer to be larger at the emitter/base junction than at the collector/base junction. The graded bandgap can increase DC current gain and speed of the device. A metalorganic chemical vapor deposition method of preparing InP heterojunction bipolar transistors having a base layer with a relatively high concentration of carbon dopant. The high carbon dopant concentration lowers the base sheet resistivity and turn-on voltage of the device.