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Denise Montesdeoca Cardenes Growth & Characterization of GaSb

Denise Montesdeoca Cardenes Growth & Characterization of GaSb Quantum Dots for Intermediate Band Solar Cell Supervisors : Anthony Krier, Peter Carrington Mid Term Meeting London 7th-8th Dec 2016. Spain, Canary Islands. Madrid 2009-2013: Physics degree (UAM).

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Denise Montesdeoca Cardenes Growth & Characterization of GaSb

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  1. Denise Montesdeoca Cardenes Growth & Characterization of GaSb Quantum DotsforIntermediate Band Solar Cell Supervisors: Anthony Krier, Peter Carrington MidTerm Meeting London 7th-8th Dec 2016 Spain, Canary Islands

  2. Madrid 2009-2013: Physics degree (UAM). Project: “P-doping with Zn on GaAs by MBE” (Basilio J. Garcia). Spain, Canary Islands P-doping in Zn was required for building mismatched alloys with Intermediate band behaviour.

  3. Madrid 2013-2014: Physics Master Degree (UAM+ICMM): Advanced Materials. Project: “Optical properties of Photonic glasses” ( Alvaro Blanco). 2014- 2015: Employer in the Photonic Crystal group (ICMM). Spain, Canary Islands

  4. Workpackage 3: Materialsforenergy • Growth & Characterization of GaSbQuantum Dots • forIntermediate Band Solar Cell • MBE growth of quantum structuresforincreasingefficiency. • Characterization of electrical and spectralproperties. • Study of Intermediateband behaviour. Top Cap: 100nm Spacer Layer GaSb QD GaSb Spacer Layer GaSb QD GaSb Buffer: 100nm GaAs(n) Substrate

  5. Understanding efficiency limit in Single Junction CB • 1. VOC=EG • 2. ISC = Isc(EG) • Single Junction Ideal SC limitedby: • Transmissionlosses • Thermalizationlosses EG Theory: ηSJ <31% Real: ηSJ =25% Si technology VB

  6. Alternative to Single Junction: Multijunction Solar Cell Tandem/stacked cells have produced record efficiencies by splitting the solar spectrum. • Expensive and limited to concentrator systems. Theory: ηMJ <50% Real: ηMJ =30%

  7. Twooperatingprinciples of IBSC: • VocConservation: • 3 Fermi levels( EF,C EF,V EF,IB) • Partialfilling of IB • 2) Two-PhotonSubbandgapPhoto-Current (TPPC): • - No overlapping of absorptioncoefficient • - Partiallyfilled IB Looking for high efficiency: Intermediate Band CB • 1. VOC=EG • 2. ISC = Isc(EG) + Isc(EH) +Isc(EH+EL) • Intermediate Band Gap Ideal SC: • More photons absorbed. • Lessphotonsthermalized. • Theory: ηSJ< ηIB=47% • IB needs to be partiallyfilled EH EG IB EL VB The Solar Energy Institute in Madrid Luque and Marti, Phys. Rev. Lett. 78 (1997) 5014

  8. MBE growth of GaSb QR/QD stacks for SC

  9. Characterization of GaSb/GaAs QD SC WL VOC drops EQE(%) QD GaAs Ref x5 x10 Wavelength (nm) • VOC drops when GaSb QD are incorporated. • Sub-bandgap photocurrent is detected: WL & QD.

  10. Intermediate Band behaviour on GaSb/GaAs SC 16K EG EH Source 1+2 Source 1 With a single Monochromatic light the photoresponse is limited until 0.8eV (1550nm). Source 1

  11. Intermediate Band behaviour on GaSb/GaAs SC 16K EG + EH EL Source 1+2 Source 1 With a secondary source the IB is photofilled enhancing the EQE beyond 0.6eV (2070nm). Source 1 +2

  12. Future work Ideal intermediate band requires interaction between QD layers. As closer the stacks are larger is the coupling and miniband can be formed. Redshift of PL emission By decreasing the Cap the energy of the GL drops. Similar behaviour is expected when QD states couple.

  13. Summary • Solar Cells grown containing GaSb QR by MBE. • GaSb QR identified by TEM, XRD and PL revealing WL. • IB behaviour observed by illuminating with a secondary source. • IV curves confirm that Voc is not conserved by adding QR in the SC. • Work in progress • PL study of Miniband formation by decreasing QD Cap. • Lifetime and photoreflectance study at Tyndall(Secondment 2017). • Modelling IBSC with Tyndall (Secondment 2017). • TEM characterization of the Stack of QDs (UCA, Cadiz). • Study the effect of the incorporation of nitrides in the QD.

  14. Skills Acquired PL (4K) XRD GROWTH IV EQE MODELLING 2 PHOTON SET UP PROCESSING

  15. Outputs • Talks at PROMIS Networks • “GaSb/GaAs Quantum Dot Solar Cell” at Cadiz PROMIS Workshop, Cadiz (Spain), 4th-6th May 2016. • “Two photon photocurrent in GaSb/GaAs Intermediate Band Solar Cell” at Montpellier PROMIS Workshop, Montpellier (France), 30th Aug-3rd Sept 2016. • Posters • “GaSb/GaAs Quantum Dot Solar Cell” at Material Science Institute, Lancaster University (Lancaster), 5th-6th April 2016. • “Two photon photocurrent in GaSb/GaAs Intermediate Band Solar Cell” at MBE16, Montpellier, 1st-5th Aug 2016;. • “GaSb/GaAs Intermediate Band Solar Cell” at Photovoltaic Workshop, Imperial College (London), 15th-16th Sept 2016. • Outreach • Webcast on Photonics: “Solar cells”. • Participation on “Day of Photonics”.

  16. Future aspirations • Publish high impact papers. • Present talks at international conferences: • PVTC2017: The Photovoltaic Technical Conference, 26-28 April (Marseille). • MBE2018: International conference in Molecular Beam Epitaxy Sept, Sept (Shanghai). • Finding a postdoc/ fellowship application/ researcher in company. • Obtain a good job in academic/industry.

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