A5015508724- solar cell performance optimization
- Semiconductor Quantum Structures and Devices
- Chalcogenide Semiconductor Thin Films
- Nanowire Synthesis and Applications
- Magnetic and transport properties of perovskites and related materials
- Semiconductor materials and interfaces
- Silicon and Solar Cell Technologies
- Shape Memory Alloy Transformations
- Rare-earth and actinide compounds
- Semiconductor materials and devices
- Ferroelectric and Piezoelectric Materials
- Superconductivity in MgB2 and Alloys
- Iron-based superconductors research
- Integrated Circuits and Semiconductor Failure Analysis
- Magnetic properties of thin films
- Magnetic Properties and Applications
- Thermal Expansion and Ionic Conductivity
- Ion-surface interactions and analysis
- Heusler alloys: electronic and magnetic properties
- Magnetic Properties of Alloys
- Thermodynamic and Structural Properties of Metals and Alloys
The Ohio State University
2017-2024
Southern Illinois University Carbondale
2018
Louisiana State University
2014-2018
By means of alloying appropriate amounts MnNiSi and MnFeGe, materials are found that undergo a paramagnetic to ferromagnetic transition close room temperature, accompanied by huge volume change. Thanks this change, application moderate pressures leads remarkable enhancement the magnetocaloric response. Work like may open new opportunities in development solid-state magnetic refrigeration devices.
(MnNiSi)1−x(FeCoGe)x undergoes a magnetostructural phase transition near room temperature that is acutely sensitive to applied hydrostatic pressure, which presents as marked shift in the martensitic (TM) by about –7.5 K/kbar. The can therefore be induced pressure or magnetic field. barocaloric and magnetocaloric effects were measured across TM (for sample with x = 0.38), corresponding entropy changes +74 J/kg K (P 2.7 kbar) –58 (μ0 H 5 T), respectively. It was observed change increases...
The isostructural alloying of two compounds with different magnetic and thermo-structural properties has resulted in a new system, (MnNiSi)1−x(FeCoGe)x, that exhibits large magnetocaloric effects acute sensitivity to both compositional variation applied hydrostatic pressure. maximum isothermal entropy change reaches value −ΔSmax = 143.7 J/kg K for field ΔB 5 T at atmospheric first-order magnetostructural transition responsible the shifts lower temperature pressure (∼−10 K/kbar) but maintains −ΔSmax.
A novel physical phenomenon has been observed that resembles a large asymmetric switchinglike magnetoresistance at low applied fields in bulk metamagnetic Heusler alloys. thermally activated isothermal forward transition with signature of pronounced time-dependent relaxation was B-substituted off-stoichiometric Ni-Mn-In alloy, whereas the reverse exhibited usual athermal behavior no thermal activation. The asymmetry between and transitions resulted switchinglike, low-field...
The novel use of a GaAsyP1–y/GaP compressively strained superlattice (CSS) to provide enhanced control over misfit dislocation (MD) evolution and threading density (TDD) during GaP/Si metamorphic heteroepitaxy is demonstrated. Insertion the CSS just after critical thickness, thus prior substantial introduction, found yield significantly reduced TDD in relaxed, 500 nm thick, n-type versus comparable samples. impact period count on average overall network morphology was examined, supported by...
We report here on progress made in the development of >20% efficient monolithic epitaxial III-V/Si tandem solar cells. Following our prior demonstration a GaAs0.75P0.25/Si cell with verified AM1.5G efficiency 20.1%, we have undertaken intensive efforts aimed at optimization top and bottom subcells, involving both materials quality improvement detailed device structure refinement. To date thus demonstrated 21.8% cells making use an optimized, but still defect-limited GaAsP combined simple...
A rear-emitter (rear-junction) n-on-p+ device design was investigated for use in metamorphic monolithic III-V/Si tandem solar cells as an alternative to the traditional front-emitter (front-junction) n+-on-p potentially greater resistance threading dislocation-induced performance degradation. comparison of MOCVD-grown rearversus 1.7-eV bandgap GaAs <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.75</sub> P...
This article highlights the critical role of window design on short circuit carrier collection in rear-emitter solar cells, as demonstrated through modeling and experiment using metamorphic GaAs <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">y</sub> P xmlns:xlink="http://www.w3.org/1999/xlink">1-y</sub> . Ultimately, if is not carefully considered, surface depletion caused by Fermi level pinning at window/air interface can extend into regions...
A high-performance metamorphic Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.2</sub> Ga xmlns:xlink="http://www.w3.org/1999/xlink">0.8</sub> As xmlns:xlink="http://www.w3.org/1999/xlink">0.75</sub> P xmlns:xlink="http://www.w3.org/1999/xlink">0.25</sub> /GaAs tunnel junction structure, grown by metal-organic chemical vapor deposition, was designed for use within GaAs /Si tandem solar cells. Optimized growth conditions were determined high...
Significant performance improvement in a top cell isotype for GaAs <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.75</sub> P xmlns:xlink="http://www.w3.org/1999/xlink">0.25</sub> /Si tandem solar was achieved using model-driven optimization process. Physics-based TCAD software used to extract key materials parameters via quantum efficiency curve fitting against reference prototype device. These were then guide the of three aspects device...
Detailed loss analysis of our previously reported 21.8% (unverified) monolithic GaAsP/Si tandem cells has identified and quantified three main mechanisms limiting cell performance: dislocation mediated voltage current losses, improper bandgap profile, insufficient rear passivation. This was recently used to redesign the device structure, yielding a substantial performance improvement 23.4% AM1.5G. The largest area in Voc 1.73V, an increase 70 mV versus previous results, enabled by -2x...
Rear-emitter n/p <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> cells were investigated as an alternative to conventional n /p front-emitter for potentially increased tolerance against threading dislocation-induced lifetime degradation. A comparison of MOCVD-grown front- and rearemitter GaAs <sub xmlns:xlink="http://www.w3.org/1999/xlink">0.75</sub> P xmlns:xlink="http://www.w3.org/1999/xlink">0.25</sub> use in III-V/Si tandem solar...
This work explores epitaxially integrated distributed Bragg reflectors (DBR) as a strategy to mitigate the impact of threading dislocations on performance monolithic GaAs0.75P0.25/Si tandem solar cells. The constraints present because materials availability and optical transmission profile GaAs0.75P0.25 top cell require use an enhanced bandwidth DBR design achieved by combining two narrow-band DBRs with different central wavelengths. this structure JSC, along competing effects dislocation...
For optimizing III-V/GaP/Si tandem cells, test samples are fabricated featuring an epitaxial GaP layer on top of p-type front junction and n-type rear silicon cells. The device characterization results used to calibrate our Sentaurus model the interface recombination velocity between Si is found be 5 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sup> cm/s by fitting EQE data. To achieve a better spectral response for bottom cell,...
This work investigates >2 eV (Al)GaInP alloys grown via MOCVD for application as the top junction of IMM solar cells. We explore balancing Al content and lattice constant two complementary variables to achieve target bandgaps in one material system. Prototype cell performance defect spectroscopy (DLTS/DLOS) are used evaluate various alloys. Results thus far suggest that metamorphic GaInP is most promising route a high-performance up until becomes indirect.
This work investigates two conceptually different approaches, both based on the AlGaInP alloy family, to produce metal-organic chemical vapor deposition grown 2.05 eV direct bandgap materials for use in top cell of AM0 multijunction solar cells. The first approach achieves target via (Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.32</sub> Ga xmlns:xlink="http://www.w3.org/1999/xlink">0.68</sub> )...
A high-performance metamorphic Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.2</sub> Ga xmlns:xlink="http://www.w3.org/1999/xlink">0.8</sub> As xmlns:xlink="http://www.w3.org/1999/xlink">0.75</sub> P xmlns:xlink="http://www.w3.org/1999/xlink">0.25</sub> /GaAs heterojunction tunnel junction structure was developed for application to monolithic epitaxial GaAs /Si 1.7 eV/1.1 eV bandgap tandem solar cells produced via metal-organic chemical...
Historically, the performance of monolithically-integrated GaAsP/Si tandem solar cells has been limited by presence elevated TDD in GaAsP subcell. However, our recent development low-TDD virtual substrates greatly improved near-term potential for achieving high efficiency devices. In this work, efforts employing new platform will be presented. First, current certified record cell (23.4% AM1.5G) is briefly analyzed, identifying root cause critical fill factor losses, which turn informs...
Ga <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.51</sub> In xmlns:xlink="http://www.w3.org/1999/xlink">0.49</sub> P solar cells with compositionally-graded (Al xmlns:xlink="http://www.w3.org/1999/xlink">z</sub> G xmlns:xlink="http://www.w3.org/1999/xlink">a1-z</sub> )xln xmlns:xlink="http://www.w3.org/1999/xlink">1-x</sub> window-emitter structures, both lattice-matched and pseudomorphically (tensile) strained, were grown via molecular beam...
III-V/Si dual junction (2J) tandem photovoltaics with potential for eventual application to (aero)space deployment have been under development. Full 2J devices 16-18% AM0 efficiency demonstrated. Temperature dependent LIV and initial characterization related space applications also conducted. Further development of the subcomponents offer a promising pathway efficiencies >25%.
Metamorphic III-V/Si materials with low threading dislocation density (TDD) are critical to realizing high-efficiency multijunction photovoltaics. In pursuit of a dual junction design GaAs <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.75</sub> P xmlns:xlink="http://www.w3.org/1999/xlink">0.25</sub> top epitaxially integrated on Si bottom junction, we report progress made in the development GaP/Si and...