Emily Warmann - Academia.edu (original) (raw)

Papers by Emily Warmann

Research paper thumbnail of Energy production advantage of independent subcell connection for multijunction photovoltaics

Energy Science & Engineering, 2016

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Design improvements for the polyhedral specular reflector spectrum-splitting module for ultra-high efficiency (>50%)

2014 Ieee 40th Photovoltaic Specialist Conference, Jun 1, 2014

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Virtual substrates for epitaxial growth and methods of making the same

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Polyhedral Specular Reflector Design for Ultra-High SpectrumSplitting Solar Module Efficiencies (>50%)

ABSTRACT One pathway to achieving ultra-high solar efficiencies (<50%) is employing a spec... more ABSTRACT One pathway to achieving ultra-high solar efficiencies (<50%) is employing a spectrum splitting optical element with at least 6 subcells and significant concentration (100-500 suns). We propose a design to meet these criteria, employing specular reflection to split and divide the light onto appropriate subcells. The polyhedral specular reflector incorporates a high index parallelepiped with seven subcells. The subcells are placed around the parallelepiped such that light entering at normal incidence encounters the subcells in order from highest to lowest bandgap, with the ray path reflecting at a 90° angle until the light is fully absorbed. Previous studies of the design have shown that concentration and filters are necessary to achieve high efficiencies and thus the current iteration of the design employs shortpass filters and two stages of concentration. Ray tracing of the current iteration shows exceeding 50% efficiency is possible for current subcell qualities with perfect shortpass filters while 50% module efficiencies are only possible for very high quality (<6% ERE) subcells with commercially available shortpass filters. However, even with commercially available filters and achievable subcell quality, ray tracing results show very high (<43%) module efficiency.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Routes to Ultrahigh Efficiency Photovoltaic and Photoelectrochemical Devices

Bookmarks Related papers MentionsView impact

Research paper thumbnail of System for contact printing

Bookmarks Related papers MentionsView impact

Research paper thumbnail of A New Paradigm for Multijunction Solar Cells

We propose an approach for a multijunction solar cell (MJSC) based on direct band gap InAlAs/InGa... more We propose an approach for a multijunction solar cell (MJSC) based on direct band gap InAlAs/InGaP/InGaAsP/InGaAs alloys. Device simulations indicate that the proposed design can achieve over 50 {\%} efficiency at 100-suns illumination by using an alloy combination ...

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Design improvements for the polyhedral specular reflector spectrum-splitting module for ultra-high efficiency (>50%)

2014 IEEE 40th Photovoltaic Specialist Conference (PVSC), 2014

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Ray trace optimization of a light trapping filtered concentrator for spectrum splitting photovoltaics

2014 IEEE 40th Photovoltaic Specialist Conference (PVSC), 2014

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Optoelectronic design of multijunction wire-array solar cells

2011 37th IEEE Photovoltaic Specialists Conference, 2011

(2011) Turner-Evans et al. PVSC 37. Read by researchers in: 100% Engineering. Microwire solar cel... more (2011) Turner-Evans et al. PVSC 37. Read by researchers in: 100% Engineering. Microwire solar cells have demonstrated promising optical and photovoltaic performance in arrays of single junction Si wires. Seeking higher efficiencies, we have numerically investigated III-V on.. ...

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Photovoltaic efficiencies in lattice-matched III-V multijunction solar cells with unconventional lattice parameters

2011 37th IEEE Photovoltaic Specialists Conference, 2011

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Spectrum splitting photovoltaics: Materials and device parameters to achieve ultrahigh system efficiency

2013 IEEE 39th Photovoltaic Specialists Conference (PVSC), 2013

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Spectrum splitting photovoltaics: Polyhedral specular reflector design for ultra-high efficiency modules

2013 IEEE 39th Photovoltaic Specialists Conference (PVSC), 2013

ABSTRACT A design for ultra-high efficiency solar modules (>50%) using spectrum splitting ... more ABSTRACT A design for ultra-high efficiency solar modules (>50%) using spectrum splitting is proposed. In the polyhedral specular reflector design, seven subcells are arranged around a solid parallelepiped. Incident light enters the parallelepiped and is directed via specular reflection onto each subcell in order from highest to lowest bandgap. We analyze optical losses due to external concentration and parasitic absorption and optimize the design for >50% module efficiency. We find that moderate concentration designs (90-170x) with a high index parallelepiped and perfect shortpass filters meet target efficiencies and demonstrate an initial design.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Spectrum splitting photovoltaics: light trapping filtered concentrator for ultrahigh photovoltaic efficiency

High and Low Concentrator Systems for Solar Electric Applications VIII, 2013

ABSTRACT While monolithic multijunction solar cell approaches have been quite successful, current... more ABSTRACT While monolithic multijunction solar cell approaches have been quite successful, current and lattice matching requirements limit the maximum possible achievable efficiencies. Spectrum splitting, where light is optically distributed among subcells with differing bandgaps, avoids these constraints and offers a route to achieving higher efficiencies (<50%). We investigate a spectrum splitting approach where concentrated sunlight is trapped in a textured dielectric slab and then selectively coupled into underlying solar cells of different bandgaps through omnidirectional filters. We develop a multipass optical model to find regimes of high optical efficiency based on parameters such as slab refractive index, number of subcells, and angle restriction of light escape from the slab. Based on these results and filter design considerations, we describe a specific design featuring a textured slab of SiO2 coated with angle restricting incoupling elements based on compound parabolic concentrators and three underlying multijunction junction solar cells, for a total of eight junctions with bandgaps ranging from 2.2eV to 0.7. Using the multipass model in conjunction with modified detailed balance calculations, we find module efficiencies exceeding 50% are possible with an acceptance angle restricted to 20° or less and concentrations of a few hundred suns with ideal omnidirectional filters. Finally as proof of concept, we design a full set of omnidirectional filters for this design. Based on alternating layers of TiO2 and SiO2, we achieve angle averaged reflectivity greater than 90% within the reflection band and angle averaged transmission of approximately 90% within the transmission band for the long pass filter, for nearly 48% receiver efficiency.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Polyhedral specular reflector design for ultra high spectrum splitting solar module efficiencies (>50%)

High and Low Concentrator Systems for Solar Electric Applications VIII, 2013

ABSTRACT One pathway to achieving ultra-high solar efficiencies (<50%) is employing a spec... more ABSTRACT One pathway to achieving ultra-high solar efficiencies (<50%) is employing a spectrum splitting optical element with at least 6 subcells and significant concentration (100-500 suns). We propose a design to meet these criteria, employing specular reflection to split and divide the light onto appropriate subcells. The polyhedral specular reflector incorporates a high index parallelepiped with seven subcells. The subcells are placed around the parallelepiped such that light entering at normal incidence encounters the subcells in order from highest to lowest bandgap, with the ray path reflecting at a 90° angle until the light is fully absorbed. Previous studies of the design have shown that concentration and filters are necessary to achieve high efficiencies and thus the current iteration of the design employs shortpass filters and two stages of concentration. Ray tracing of the current iteration shows exceeding 50% efficiency is possible for current subcell qualities with perfect shortpass filters while 50% module efficiencies are only possible for very high quality (<6% ERE) subcells with commercially available shortpass filters. However, even with commercially available filters and achievable subcell quality, ray tracing results show very high (<43%) module efficiency.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Nanophotonic design principles for ultrahigh efficiency photovoltaics

ABSTRACT To date, solar-cell efficiencies have remained well below the thermodynamic limits. Howe... more ABSTRACT To date, solar-cell efficiencies have remained well below the thermodynamic limits. However new nanophotonic and microphotonic approaches to light management that systematically minimize thermodynamic losses can enable ultrahigh efficiencies previously considered to be out of reach.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Routes to ultrahigh efficiency photovoltaic and photoelectrochemical devices

2014 IEEE Photonics Conference, 2014

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Spectrum-splitting photovoltaics: Holographic spectrum splitting in eight-junction, ultra-high efficiency module

2013 IEEE 39th Photovoltaic Specialists Conference (PVSC), 2013

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Full spectrum ultrahigh efficiency photovoltaics

2013 IEEE 39th Photovoltaic Specialists Conference (PVSC), 2013

ABSTRACT Future photovoltaic systems can be greatly benefited by modules that exhibit simultaneou... more ABSTRACT Future photovoltaic systems can be greatly benefited by modules that exhibit simultaneously ultrahigh efficiency (> 50%) and low-cost (<; $0.50/Wp) to enable sharp reductions in the levelized cost of electricity. A 'full spectrum' photovoltaic module, which takes advantage of advances in low-cost III-V compound cell fabrication and emerging optical and electronic fabrication/assembly methods, features 6-15 independently connected subcells in a spectrum splitting, concentrating photovoltaic receiver. Module architectures utilizing independently connected single junction and multijunction subcells allow flexibility in subcell selection for optimal energy bandgaps and fabrication, and also reduce the constraints posed by current matching requirements. Several different spectrum-splitting optical architectures designed for systems with many (>6) subcells are possible, including designs based on holographic spectrum splitting, specular reflection in dielectric polyhedra and light trapping textured filtered dielectric slabs that perform as nonimaging concentrators.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of A New Paradigm for Multijunction Solar Cells

We propose an approach for a multijunction solar cell (MJSC) based on direct band gap InAlAs/InGa... more We propose an approach for a multijunction solar cell (MJSC) based on direct band gap InAlAs/InGaP/InGaAsP/InGaAs alloys. Device simulations indicate that the proposed design can achieve over 50 {\%} efficiency at 100-suns illumination by using an alloy combination ...

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Energy production advantage of independent subcell connection for multijunction photovoltaics

Energy Science & Engineering, 2016

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Design improvements for the polyhedral specular reflector spectrum-splitting module for ultra-high efficiency (>50%)

2014 Ieee 40th Photovoltaic Specialist Conference, Jun 1, 2014

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Virtual substrates for epitaxial growth and methods of making the same

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Polyhedral Specular Reflector Design for Ultra-High SpectrumSplitting Solar Module Efficiencies (>50%)

ABSTRACT One pathway to achieving ultra-high solar efficiencies (<50%) is employing a spec... more ABSTRACT One pathway to achieving ultra-high solar efficiencies (<50%) is employing a spectrum splitting optical element with at least 6 subcells and significant concentration (100-500 suns). We propose a design to meet these criteria, employing specular reflection to split and divide the light onto appropriate subcells. The polyhedral specular reflector incorporates a high index parallelepiped with seven subcells. The subcells are placed around the parallelepiped such that light entering at normal incidence encounters the subcells in order from highest to lowest bandgap, with the ray path reflecting at a 90° angle until the light is fully absorbed. Previous studies of the design have shown that concentration and filters are necessary to achieve high efficiencies and thus the current iteration of the design employs shortpass filters and two stages of concentration. Ray tracing of the current iteration shows exceeding 50% efficiency is possible for current subcell qualities with perfect shortpass filters while 50% module efficiencies are only possible for very high quality (<6% ERE) subcells with commercially available shortpass filters. However, even with commercially available filters and achievable subcell quality, ray tracing results show very high (<43%) module efficiency.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Routes to Ultrahigh Efficiency Photovoltaic and Photoelectrochemical Devices

Bookmarks Related papers MentionsView impact

Research paper thumbnail of System for contact printing

Bookmarks Related papers MentionsView impact

Research paper thumbnail of A New Paradigm for Multijunction Solar Cells

We propose an approach for a multijunction solar cell (MJSC) based on direct band gap InAlAs/InGa... more We propose an approach for a multijunction solar cell (MJSC) based on direct band gap InAlAs/InGaP/InGaAsP/InGaAs alloys. Device simulations indicate that the proposed design can achieve over 50 {\%} efficiency at 100-suns illumination by using an alloy combination ...

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Design improvements for the polyhedral specular reflector spectrum-splitting module for ultra-high efficiency (>50%)

2014 IEEE 40th Photovoltaic Specialist Conference (PVSC), 2014

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Ray trace optimization of a light trapping filtered concentrator for spectrum splitting photovoltaics

2014 IEEE 40th Photovoltaic Specialist Conference (PVSC), 2014

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Optoelectronic design of multijunction wire-array solar cells

2011 37th IEEE Photovoltaic Specialists Conference, 2011

(2011) Turner-Evans et al. PVSC 37. Read by researchers in: 100% Engineering. Microwire solar cel... more (2011) Turner-Evans et al. PVSC 37. Read by researchers in: 100% Engineering. Microwire solar cells have demonstrated promising optical and photovoltaic performance in arrays of single junction Si wires. Seeking higher efficiencies, we have numerically investigated III-V on.. ...

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Photovoltaic efficiencies in lattice-matched III-V multijunction solar cells with unconventional lattice parameters

2011 37th IEEE Photovoltaic Specialists Conference, 2011

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Spectrum splitting photovoltaics: Materials and device parameters to achieve ultrahigh system efficiency

2013 IEEE 39th Photovoltaic Specialists Conference (PVSC), 2013

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Spectrum splitting photovoltaics: Polyhedral specular reflector design for ultra-high efficiency modules

2013 IEEE 39th Photovoltaic Specialists Conference (PVSC), 2013

ABSTRACT A design for ultra-high efficiency solar modules (>50%) using spectrum splitting ... more ABSTRACT A design for ultra-high efficiency solar modules (>50%) using spectrum splitting is proposed. In the polyhedral specular reflector design, seven subcells are arranged around a solid parallelepiped. Incident light enters the parallelepiped and is directed via specular reflection onto each subcell in order from highest to lowest bandgap. We analyze optical losses due to external concentration and parasitic absorption and optimize the design for >50% module efficiency. We find that moderate concentration designs (90-170x) with a high index parallelepiped and perfect shortpass filters meet target efficiencies and demonstrate an initial design.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Spectrum splitting photovoltaics: light trapping filtered concentrator for ultrahigh photovoltaic efficiency

High and Low Concentrator Systems for Solar Electric Applications VIII, 2013

ABSTRACT While monolithic multijunction solar cell approaches have been quite successful, current... more ABSTRACT While monolithic multijunction solar cell approaches have been quite successful, current and lattice matching requirements limit the maximum possible achievable efficiencies. Spectrum splitting, where light is optically distributed among subcells with differing bandgaps, avoids these constraints and offers a route to achieving higher efficiencies (<50%). We investigate a spectrum splitting approach where concentrated sunlight is trapped in a textured dielectric slab and then selectively coupled into underlying solar cells of different bandgaps through omnidirectional filters. We develop a multipass optical model to find regimes of high optical efficiency based on parameters such as slab refractive index, number of subcells, and angle restriction of light escape from the slab. Based on these results and filter design considerations, we describe a specific design featuring a textured slab of SiO2 coated with angle restricting incoupling elements based on compound parabolic concentrators and three underlying multijunction junction solar cells, for a total of eight junctions with bandgaps ranging from 2.2eV to 0.7. Using the multipass model in conjunction with modified detailed balance calculations, we find module efficiencies exceeding 50% are possible with an acceptance angle restricted to 20° or less and concentrations of a few hundred suns with ideal omnidirectional filters. Finally as proof of concept, we design a full set of omnidirectional filters for this design. Based on alternating layers of TiO2 and SiO2, we achieve angle averaged reflectivity greater than 90% within the reflection band and angle averaged transmission of approximately 90% within the transmission band for the long pass filter, for nearly 48% receiver efficiency.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Polyhedral specular reflector design for ultra high spectrum splitting solar module efficiencies (>50%)

High and Low Concentrator Systems for Solar Electric Applications VIII, 2013

ABSTRACT One pathway to achieving ultra-high solar efficiencies (<50%) is employing a spec... more ABSTRACT One pathway to achieving ultra-high solar efficiencies (<50%) is employing a spectrum splitting optical element with at least 6 subcells and significant concentration (100-500 suns). We propose a design to meet these criteria, employing specular reflection to split and divide the light onto appropriate subcells. The polyhedral specular reflector incorporates a high index parallelepiped with seven subcells. The subcells are placed around the parallelepiped such that light entering at normal incidence encounters the subcells in order from highest to lowest bandgap, with the ray path reflecting at a 90° angle until the light is fully absorbed. Previous studies of the design have shown that concentration and filters are necessary to achieve high efficiencies and thus the current iteration of the design employs shortpass filters and two stages of concentration. Ray tracing of the current iteration shows exceeding 50% efficiency is possible for current subcell qualities with perfect shortpass filters while 50% module efficiencies are only possible for very high quality (<6% ERE) subcells with commercially available shortpass filters. However, even with commercially available filters and achievable subcell quality, ray tracing results show very high (<43%) module efficiency.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Nanophotonic design principles for ultrahigh efficiency photovoltaics

ABSTRACT To date, solar-cell efficiencies have remained well below the thermodynamic limits. Howe... more ABSTRACT To date, solar-cell efficiencies have remained well below the thermodynamic limits. However new nanophotonic and microphotonic approaches to light management that systematically minimize thermodynamic losses can enable ultrahigh efficiencies previously considered to be out of reach.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Routes to ultrahigh efficiency photovoltaic and photoelectrochemical devices

2014 IEEE Photonics Conference, 2014

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Spectrum-splitting photovoltaics: Holographic spectrum splitting in eight-junction, ultra-high efficiency module

2013 IEEE 39th Photovoltaic Specialists Conference (PVSC), 2013

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Full spectrum ultrahigh efficiency photovoltaics

2013 IEEE 39th Photovoltaic Specialists Conference (PVSC), 2013

ABSTRACT Future photovoltaic systems can be greatly benefited by modules that exhibit simultaneou... more ABSTRACT Future photovoltaic systems can be greatly benefited by modules that exhibit simultaneously ultrahigh efficiency (> 50%) and low-cost (<; $0.50/Wp) to enable sharp reductions in the levelized cost of electricity. A 'full spectrum' photovoltaic module, which takes advantage of advances in low-cost III-V compound cell fabrication and emerging optical and electronic fabrication/assembly methods, features 6-15 independently connected subcells in a spectrum splitting, concentrating photovoltaic receiver. Module architectures utilizing independently connected single junction and multijunction subcells allow flexibility in subcell selection for optimal energy bandgaps and fabrication, and also reduce the constraints posed by current matching requirements. Several different spectrum-splitting optical architectures designed for systems with many (>6) subcells are possible, including designs based on holographic spectrum splitting, specular reflection in dielectric polyhedra and light trapping textured filtered dielectric slabs that perform as nonimaging concentrators.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of A New Paradigm for Multijunction Solar Cells

We propose an approach for a multijunction solar cell (MJSC) based on direct band gap InAlAs/InGa... more We propose an approach for a multijunction solar cell (MJSC) based on direct band gap InAlAs/InGaP/InGaAsP/InGaAs alloys. Device simulations indicate that the proposed design can achieve over 50 {\%} efficiency at 100-suns illumination by using an alloy combination ...

Bookmarks Related papers MentionsView impact