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  • JOURNAL ARTICLE
    Alonso-Alvarez D, Ekins-Daukes N, 2016,

    Photoluminescence-Based Current-Voltage Characterization of Individual Subcells in Multijunction Devices

    , IEEE JOURNAL OF PHOTOVOLTAICS, Vol: 6, Pages: 1004-1011, ISSN: 2156-3381
  • JOURNAL ARTICLE
    Alonso-Álvarez D, Ekins-Daukes N, 2016,

    SPICE modelling of photoluminescence and electroluminescence based current-voltage curves of solar cells for concentration applications

    , Journal of Green Engineering, Vol: 5, Pages: 33-47, ISSN: 1904-4720

    © 2016 River Publishers. All rights reserved. Quantitative photoluminescence (PL) or electroluminescence (EL) experiments can be used to probe fast and in a non-destructive way the currentvoltage (IV) characteristics of individual subcells in a multi-junction device, information that is, otherwise, not available. PL-based IV has the advantage that it is contactless and can be performed even in partly finished devices, allowing for an early diagnosis of the expected performance of the solar cells in the production environment. In this work we simulate the PL- and ELbased IV curves of single junction solar cells to assess their validity compared with the true IV curve and identify injection regimes where artefacts might appear due to the limited in-plane carrier transport in the solar cell layers. We model the whole photovoltaic device as a network of sub-circuits, each of them describing the solar cell behaviour using the two diode model. The subcircuits are connected to the neighbouring ones with a resistor, representing the in-plane transport in the cell. The resulting circuit, involving several thousand sub-circuits, is solved using SPICE.
  • CONFERENCE PAPER
    Richards RD, Harun F, Cheong JS, Mellor A, Hylton NP, Wilson T, Thomas T, Ekins-Daukes NJ, David JPRet al., 2016,

    GaAsBi: An Alternative to InGaAs Based Multiple Quantum Well Photovoltaics

    , 43rd IEEE Photovoltaic Specialists Conference (PVSC), Publisher: IEEE, Pages: 1135-1137, ISSN: 0160-8371
  • JOURNAL ARTICLE
    Roucka R, Clark A, Wilson T, Thomas T, Fuhrer M, Ekins-Daukes N, Johnson A, Hoffman R, Begarney Det al., 2016,

    Demonstrating Dilute-Tin Alloy SiGeSn for Use in Multijunction Photovoltaics: Single- and Multijunction Solar Cells With a 1.0-eV SiGeSn Junction

    , IEEE JOURNAL OF PHOTOVOLTAICS, Vol: 6, Pages: 1025-1030, ISSN: 2156-3381
  • JOURNAL ARTICLE
    Sugiyama M, Fujii H, Katoh T, Toprasertpong K, Sodabanlu H, Watanabe K, Alonso-Alvarez D, Ekins-Daukes NJ, Nakano Yet al., 2016,

    Quantum wire-on-well (WoW) cell with long carrier lifetime for efficient carrier transport

    , PROGRESS IN PHOTOVOLTAICS, Vol: 24, Pages: 1606-1614, ISSN: 1062-7995
  • CONFERENCE PAPER
    Wilson T, Thomas T, Fuhrer M, Ekins-Daukes NJ, Roucka R, Clark A, Johnson A, Hoffman R, Begarney Det al., 2016,

    Single and Multi-Junction Solar Cells Utilizing a 1.0 eV SiGeSn Junction

    , 12th International Conference on Concentrator Photovoltaic Systems (CPV), Publisher: AMER INST PHYSICS, ISSN: 0094-243X
  • CONFERENCE PAPER
    Alonso Alvarez D, Lackner D, Philipps SP, Bett AW, Ekins-Daukes NJet al., 2015,

    Photoluminescence-Based Current-Voltage Characterisation of Individual Subcells in Multi-Junction Devices

    , 31st European Photovoltaic Solar Energy Conference and Exhibition, Publisher: European Photovoltaic Solar Energy Conference and Exhibition, Pages: 1509-1513

    We demonstrate a photoluminescence based, contactless method to determine the current-voltage characteristics of the individual subcells in a multi-junction solar cell. The method, furthers known results for single junction devices and relies upon the reciprocity relation between the absorption and emission properties on a solar cell. Laser light with a suitable energy is used to excite carriers selectively in one junction and the internal voltages are deduced from the intensity of the resulting luminescence. The IV curves obtained this way on 1J, 2J and 6J devices are compared to those obtained using electroluminescence. Good agreement is obtained at high injection conditions while discrepancies at low injection are attributed to in-plane carrier transport.
  • JOURNAL ARTICLE
    Emmott CJM, Roehr JA, Campoy-Quiles M, Kirchartz T, Urbina A, Ekins-Daukes NJ, Nelson Jet al., 2015,

    Organic photovoltaic greenhouses: a unique application for semi-transparent PV?

    , ENERGY & ENVIRONMENTAL SCIENCE, Vol: 8, Pages: 1317-1328, ISSN: 1754-5692
  • JOURNAL ARTICLE
    Thomas T, Mellor A, Hylton NP, Fuehrer M, Alonso-Alvarez D, Braun A, Ekins-Daukes NJ, David JPR, Sweeney SJet al., 2015,

    Requirements for a GaAsBi 1eV sub-cell in a GaAs-based multi-junction solar cell

    , SEMICONDUCTOR SCIENCE AND TECHNOLOGY, Vol: 30, ISSN: 0268-1242
  • CONFERENCE PAPER
    Thomas T, Wilson T, Fuhrer M, Hylton N, Ekins-Daukes N, Tan KH, Li D, Wicaksono S, Loke WK, Fatt YS, Johnson Aet al., 2015,

    Use of Double Band Anti-Crossing to Control Optical Absorption of GaAsSbN for Multi-Junction Solar Cells

    , 31st European Photovoltaic Solar Energy Conference and Exhibition
  • JOURNAL ARTICLE
    Wilson T, Thomas T, Führer M, Ekins-Daukes NJet al., 2015,

    Addressing reflectivity losses in multijunction solar cells to achieve 50% power conversion efficiency

    , Materials Research Innovations, Vol: 19, Pages: 503-507, ISSN: 1432-8917

    © W. S. Maney & Son Ltd. 2016. As we progress towards the next generation of multi-junction solar cell technology, incorporating four junctions or more, current dual-layer coating technology applied to commercially available triple-junction solar cells will become inadequate as the current matching between the lower sub cells, absorbing in the infrared, becomes more critical. Here we present some single, double and triple layer anti-reflection coatings for comparison, optimised using a genetic algorithm, for both triple-and quad-junction solar cell architectures. It is found that there is a small increase in power conversion efficiency between the dual and triple layer coatings applied to the triple-junction structure (0.7%), however this is more than doubled when optimised dual and triple layer coatings are applied to the quad-junction device (1.5%). This work demonstrates the effectiveness of a well-optimised multi-layer anti-reflection coating in realising an appreciable increase in device performance in the next generation of multi-junction solar cells, highlighting a realistic power conversion efficiency of up to 50.35%.
  • CONFERENCE PAPER
    Alonso-Alvarez D, Fuehrer M, Thomas T, Ekins-Daukes Net al., 2014,

    Elements of modelling and design of multi-quantum well solar cells

    , 40th IEEE Photovoltaic Specialists Conference (PVSC), Publisher: IEEE, Pages: 2865-2870
  • JOURNAL ARTICLE
    Alonso-Alvarez D, Thomas T, Fuehrer M, Hylton NP, Ekins-Daukes NJ, Lackner D, Philipps SP, Bett AW, Sodabanlu H, Fujii H, Watanabe K, Sugiyama M, Nasi L, Campanini Met al., 2014,

    InGaAs/GaAsP strain balanced multi-quantum wires grown on misoriented GaAs substrates for high efficiency solar cells

    , APPLIED PHYSICS LETTERS, Vol: 105, ISSN: 0003-6951
  • JOURNAL ARTICLE
    Chan NLA, Thomas T, Fuehrer M, Ekins-Daukes NJet al., 2014,

    Practical Limits of Multijunction Solar Cell Performance Enhancement From Radiative Coupling Considering Realistic Spectral Conditions

    , IEEE JOURNAL OF PHOTOVOLTAICS, Vol: 4, Pages: 1306-1313, ISSN: 2156-3381
  • JOURNAL ARTICLE
    Piper RB, Yoshida M, Farrell DJ, Khoury T, Crossley MJ, Schmidt TW, Haque SA, Ekins-Daukes NJet al., 2014,

    Kinetic insight into bimolecular upconversion: experiment and simulation

    , RSC ADVANCES, Vol: 4, Pages: 8059-8063, ISSN: 2046-2069
  • JOURNAL ARTICLE
    Yoshida M, Amrania H, Farrell DJ, Browne B, Yoxall E, Ekins-Daukes NJ, Phillips CCet al., 2014,

    Progress Toward Realizing an Intermediate Band Solar Cell-Sequential Absorption of Photons in a Quantum Well Solar Cell

    , IEEE JOURNAL OF PHOTOVOLTAICS, Vol: 4, Pages: 634-638, ISSN: 2156-3381
  • JOURNAL ARTICLE
    Chan NLA, Young TB, Brindley HE, Ekins-Daukes NJ, Araki K, Kemmoku Y, Yamaguchi Met al., 2013,

    Validation of energy prediction method for a concentrator photovoltaic module in Toyohashi Japan

    , PROGRESS IN PHOTOVOLTAICS, Vol: 21, Pages: 1598-1610, ISSN: 1062-7995
  • JOURNAL ARTICLE
    Ekins-Daukes NJ, Lee K-H, Hirst L, Chan A, Fuehrer M, Adams J, Browne B, Barnham KWJ, Stavrinou P, Connolly J, Roberts JS, Stevens B, Airey R, Kennedy Ket al., 2013,

    Controlling radiative loss in quantum well solar cells

    , JOURNAL OF PHYSICS D-APPLIED PHYSICS, Vol: 46, ISSN: 0022-3727
  • JOURNAL ARTICLE
    Hylton NP, Li XF, Giannini V, Lee K-H, Ekins-Daukes NJ, Loo J, Vercruysse D, Van Dorpe P, Sodabanlu H, Sugiyama M, Maier SAet al., 2013,

    Loss mitigation in plasmonic solar cells: aluminium nanoparticles for broadband photocurrent enhancements in GaAs photodiodes

    , SCIENTIFIC REPORTS, Vol: 3, ISSN: 2045-2322
  • JOURNAL ARTICLE
    Li X, Hylton NP, Giannini V, Lee K-H, Ekins-Daukes NJ, Maier SAet al., 2013,

    Multi-dimensional modeling of solar cells with electromagnetic and carrier transport calculations

    , PROGRESS IN PHOTOVOLTAICS, Vol: 21, Pages: 109-120, ISSN: 1062-7995
  • JOURNAL ARTICLE
    Chan NLA, Ekins-Daukes NJ, Adams JGJ, Lumb MP, Gonzalez M, Jenkins PP, Vurgaftman I, Meyer JR, Walters RJet al., 2012,

    Optimal Bandgap Combinations-Does Material Quality Matter?

    , IEEE JOURNAL OF PHOTOVOLTAICS, Vol: 2, Pages: 202-208, ISSN: 2156-3381
  • JOURNAL ARTICLE
    Lee K-H, Barnham KWJ, Connolly JP, Browne BC, Airey RJ, Roberts JS, Fuehrer M, Tibbits TND, Ekins-Daukes NJet al., 2012,

    Demonstration of Photon Coupling in Dual Multiple-Quantum-Well Solar Cells

    , IEEE JOURNAL OF PHOTOVOLTAICS, Vol: 2, Pages: 68-74, ISSN: 2156-3381
  • JOURNAL ARTICLE
    Yoshida M, Ekins-Daukes NJ, Farrell DJ, Phillips CCet al., 2012,

    Photon ratchet intermediate band solar cells

    , APPLIED PHYSICS LETTERS, Vol: 100, ISSN: 0003-6951
  • CONFERENCE PAPER
    Adams JGJ, Browne BC, Ballard IM, Connolly JP, Chan NLA, Ioannides A, Elder W, Stavrinou PN, Barnham KWJ, Ekins-Daukes NJet al., 2011,

    Recent results for single-junction and tandem quantum well solar cells

    , 25th European Photovoltaic Solar Energy Conference and Exhibition (EU PVSEC)/5th World Conference on Photovoltaic Energy Conversion (WCPEC-5), Publisher: WILEY-BLACKWELL, Pages: 865-877, ISSN: 1062-7995
  • JOURNAL ARTICLE
    Farrell DJ, Ekins-Daukes NJ, 2011,

    Routes to High-efficiency Photovoltaic Conversion of Solar Energy

    , Modern Energy Review, Vol: 3
  • JOURNAL ARTICLE
    Farrell DJ, Takeda Y, Nishikawa K, Nagashima T, Motohiro T, Ekins-Daukes NJet al., 2011,

    A hot-carrier solar cell with optical energy selective contacts

    , APPLIED PHYSICS LETTERS, Vol: 99, ISSN: 0003-6951
  • JOURNAL ARTICLE
    Hirst LC, Ekins-Daukes NJ, 2011,

    Fundamental losses in solar cells

    , PROGRESS IN PHOTOVOLTAICS, Vol: 19, Pages: 286-293, ISSN: 1062-7995
  • JOURNAL ARTICLE
    Cheng YY, Khoury T, Clady RGCR, Tayebjee MJY, Ekins-Daukes NJ, Crossley MJ, Schmidt TWet al., 2010,

    On the efficiency limit of triplet-triplet annihilation for photochemical upconversion

    , PHYSICAL CHEMISTRY CHEMICAL PHYSICS, Vol: 12, Pages: 66-71, ISSN: 1463-9076
  • CONFERENCE PAPER
    Barnham KWJ, Adams JGJ, Elder W, Stavrinou P, Ekins-Daukes NJet al., 2009,

    Efficiency enhancement in strain-balanced quantum well solar cells via anisotropic emission

    , 24th European Photovoltaic Solar Energy Conference
  • CONFERENCE PAPER
    Barnham KWJ, Ekins-Daukes NJ, Browne B, 2009,

    Radiative limits in quantum well solar cells

    , 24th European Photovoltaic Solar Energy Conference
  • CONFERENCE PAPER
    Chatten AJ, Bose R, Farrell DJ, Pardo-Sanchez C, Pravettoni M, Mazzer M, Barnham WJet al., 2009,

    Luminescent Solar Concentrators: cylindrical design

    , 24th European Photovoltaic Solar Energy Conference
  • CONFERENCE PAPER
    Chatten AJ, Pravettoni M, Farrell DJ, Bose R, Kenny RP, Barnham Ket al., 2009,

    External quantum efficiency measurements of luminescent solar concentrators: a study of the impact of backside reflector size and shape

    , 24th European Photovoltaic Solar Energy Conference
  • JOURNAL ARTICLE
    Farrell DJ, Ekins-Daukes NJ, 2009,

    Relay dye boosts efficiency

    , NATURE PHOTONICS, Vol: 3, Pages: 373-374, ISSN: 1749-4885
  • CONFERENCE PAPER
    Adams JGJ, Barnham KWJ, Connolly JP, Hill G, Roberts JS, Tibbits TND, Geen M, Pate Met al., 2008,

    Strain-balanced quantum well concentrator cells from multiwafer production

    , ISSN: 0160-8371

    Strain-balanced quantum well solar cells with 50 quantum well layers of In0.11GaAs in the intrinsic region of a GaAs p-i-n solar cell have been studied. Devices have been taken from different positions across 4' wafers from two manufacturing runs on a multi-wafer production reactor. Growth has been compared for devices with and without distributed Bragg reflectors (DBRs), and for devices with and without stepped p-region emitters. Device quantum efficiencies and dark currents have been modeled and compared to experimental data in order to predict efficiencies at 500 suns in an AM1.5D spectrum. Suppression of the radiative recombination component of the dark current has been observed in devices with DBRs, indicating the occurrence of photon recycling. A decrease in the Shockley injection component of the dark current has been found in devices with stepped p-region emitters, as minority carriers are deflected from the surface of the device. Good uniformity of performance has been observed in devices from across the wafer despite varying DBR position, and high device yields are to be expected during manufacture. © 2008 IEEE.
  • CONFERENCE PAPER
    Barnham KWJ, Adams JGJ, Connolly JP, Calder C, Hill G, Roberts JS, Tibbits TND, Geen M, Pate Met al., 2008,

    Characterisation of Strain-Balanced Quantum Well Concentrator Cells Enhanced By Photon Recycling

    , PVSAT-4
  • CONFERENCE PAPER
    Barnham KWJ, Adams JGJ, Ginige R, Connolly JP, Ballard IM, Ekins-Daukes NJ, Hill G, Roberts JSet al., 2008,

    Single-Junction Concentrator Quantum Well Solar Cells Enhanced By Photon Recycling

    , 23rd European Photovoltaic Solar Energy Conference
  • CONFERENCE PAPER
    Barnham KWJ, Browne B, Ioannides A, Connolly J, Hill G, Roberts J, Airey R, Hill G, Smekens G, Van Begin Jet al., 2008,

    Efficiency of Tandem Quantum Well Solar Cells

    , PVSAT-4
  • CONFERENCE PAPER
    Barnham KWJ, Fuhrer MF, Connolly JP, Mazzer M, Ballard IM, Ekins-Daukes NJ, Johnson DC, Bessiere A, Roberts JS, Airey R, Calder C, Hill G, Tibbits TNDet al., 2008,

    Exciton Broadening in Quantum Well Solar Cells

    , 23rd European Photovoltaic Solar Energy Conference
  • CONFERENCE PAPER
    Bose R, Farrell DJ, Chatten AJ, Pravettoni M, Buechtemann A, Quilitz J, Fiore A, Manna L, Barnham KWJet al., 2008,

    LUMINESCENT SOLAR CONCENTRATORS: NANORODS AND RAYTRACE MODELING

    , 33rd IEEE Photovoltaic Specialists Conference, Publisher: IEEE, Pages: 24-+, ISSN: 0160-8371
  • CONFERENCE PAPER
    Browne B, Ekins-Daukes N, Ioannides A, Connolly J, Ballard I, Barnham K, Tibbits T, Pate M, Geen M, Roberts J, Hill G, Calder C, Airey R, Smekens G, Van Begin Jet al., 2008,

    Dual Multiple Quantum Well Solar Cells

    , 23rd European Photovoltaic Solar Energy Conference
  • CONFERENCE PAPER
    Browne B, Ioannides A, Connolly J, Barnham K, Roberts J, Airey R, Hill G, Smekens G, Van Begin Jet al., 2008,

    Tandem quantum well solar cells

    , ISSN: 0160-8371

    Quantum wells offer advantages in conventional bulk tandem solar cells since they allow the independent tailoring of the absorption edge of either cell with no lattice mismatch and subsequent relaxation. We describe progress in the band gap engineering of InGaP/GaAs solar cells using strain balanced quantum wells and present a tandem quantum well structure which has achieved 30.6% efficiency under 54 suns AM1.5g. This is a record for photovoltaic nanostructured devices. We predict realistic efficiencies of 34% under 600suns, AM1.5d low AOD for optimized devices. Finally, the possibility and potential gains of introducing quantum wells into both cells of an InGaP/GaAs device are discussed. © 2008 IEEE.
  • CONFERENCE PAPER
    Chatten AJ, bose, farrell, pravettoni, Buchtemann A, Quiltz J, Fiore A, Manna L, Nelson J, Alivisatos AP, Barnhamet al., 2008,

    The Effect of Size and Dopant Concentration of the Performance of Nanorod Luminescent Solar Concentrators

    , The 23rd European Photovoltaic Solar Energy Conference and Exhibition
  • CONFERENCE PAPER
    Chatten AJ, bose R, farrell D, Buchtemann A, Barnhamet al., 2008,

    The Luminescent Concentrator: Thin Films and Large Area Modelling

    , PVSAT-4
  • CONFERENCE PAPER
    Ekins-Daukes NJ, 2008,

    EVALUATION OF InGaP/In(0.01)GaAs/Ge CONCENTRATOR SYSTEM ANNUAL ENERGY YIELD AND COMPARISON TO ESTIMATES BASED ON REFERENCE SPECTRA.

    , 33rd IEEE Photovoltaic Specialists Conference, Publisher: IEEE, Pages: 383-386, ISSN: 0160-8371
  • JOURNAL ARTICLE
    Ekins-Daukes NJ, Schmidt TW, 2008,

    A molecular approach to the intermediate band solar cell: The symmetric case

    , APPLIED PHYSICS LETTERS, Vol: 93, ISSN: 0003-6951
  • CONFERENCE PAPER
    Fuhrer MF, Connolly JP, Mazzer M, Ballard IM, Johnson DC, Barnham KWJ, Bessiere A, Roberts JS, Airey R, Calder C, Hill G, Tibbits TND, Pate M, Geen Met al., 2008,

    HOT CARRIERS IN STRAIN BALANCED QUANTUM WELL SOLAR CELLS

    , 33rd IEEE Photovoltaic Specialists Conference, Publisher: IEEE, Pages: 1016-+, ISSN: 0160-8371
  • JOURNAL ARTICLE
    Johnson JC, Ballard IM, Barnham KWJ, Connolly JP, Mazzer M, Bessiere A, Calder C, Hill G, Roberts JSet al., 2007,

    Observation of photon recycling in strain-balanced quantum well solar cells

    , Applied Physics Letters, Vol: 90, Pages: 213505-213507

    Photon recycling in strain-balanced quantum well solar cells grown on distributed Bragg reflectors has been observed as a suppression of the dark current and a change in electroluminescence spectra.Comparing devices grown with and without distributed Bragg reflectors we have demonstrated up to a 33% reduction in the ideality n=1 reverse saturation current. Furthermore, to validate the observations we demonstrate how both the measured dark currents and electroluminescence spectra fit very well to a photon recycling model. Verifying our observations with the model then allows us to calculate optimized device designs.
  • JOURNAL ARTICLE
    Rohr C, Abbott P, Ballard I, Connolly JP, Barnham KWJ, Mazzer M, Button C, Nasi L, Hill G, Roberts JS, Clarke G, Ginige Ret al., 2006,

    InP-based lattice-matched InGaAsP and strain-compensated InGaAs/InGaAs quantum well cells for thermophotovoltaic applications

    , Journal of Applied Physics, Vol: 100, ISSN: 0021-8979

    Quantum well cells (QWCs) for thermophotovoltaic (TPV) applications are demonstrated in the InGaAsP material system lattice matched to the InP substrate and strain-compensated InGaAsInGaAs QWCs also on InP substrates. We show that lattice-matched InGaAsP QWCs are very well suited for TPV applications such as with erbia selective emitters. QWCs with the same effective band gap as a bulk control cell show a better voltage performance in both wide and erbialike emission. We demonstrate a QWC with enhanced efficiency in a narrow-band spectrum compared to a bulk heterostructure control cell with the same absorption edge. A major advantage of QWCs is that the band gap can be engineered by changing the well thickness and varying the composition to the illuminating spectrum. This is relatively straightforward in the lattice-matched InGaAsP system. This approach can be extended to longer wavelengths by using strain-compensation techniques, achieving band gaps as low as 0.62 eV that cannot be achieved with lattice-matched bulk material. We show that strain-compensated QWCs have voltage performances that are at least as good as, if not better than, expected from bulk control cells. © 2006 American Institute of Physics.
  • JOURNAL ARTICLE
    Bushnell D, Tibbits T, Barnham K, Connolly J, Mazzer M, Ekins-Daukes N, Roberts J, Hill G, Airey Ret al., 2005,

    Effect of well number on the performance of quantum-well solar cells

    , Journal of Applied Physics, Vol: 97

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