PROMIS A Marie SkodowskaCurie Initial Training Network Postgraduate

PROMIS A Marie Skłodowska-Curie Initial Training Network Postgraduate Research on Dilute Metamorphic Nanostructures and Metamaterials in Semiconductor Photonics Denise Montesdeoca Cardenes Spain, Canary Islands Growth & Characterization of Ga. Sb Quantum Dots for Intermediate Band Solar Cell Supervisors: Anthony Krier, Peter Carrington Mid Term Meeting London 7 th-8 th Dec 2016

PROMIS A Marie Skłodowska-Curie Initial Training Network Postgraduate Research on Dilute Metamorphic Nanostructures and Metamaterials in Semiconductor Photonics Madrid 2009 -2013: Physics degree (UAM). Spain, Canary Islands Project: “P-doping with Zn on Ga. As by MBE” (Basilio J. Garcia). P-doping in Zn was required for building mismatched alloys with Intermediate band behaviour.

PROMIS A Marie Skłodowska-Curie Initial Training Network Postgraduate Research on Dilute Metamorphic Nanostructures and Metamaterials in Semiconductor Photonics Madrid 2013 -2014: Physics Master Degree (UAM+ICMM): Advanced Materials. Spain, Canary Islands Project: “Optical properties of Photonic glasses” ( Alvaro Blanco). 2014 - 2015: Employer in the Photonic Crystal group (ICMM).

PROMIS A Marie Skłodowska-Curie Initial Training Network Postgraduate Research on Dilute Metamorphic Nanostructures and Metamaterials in Semiconductor Photonics Workpackage 3: Materials for energy Growth & Characterization of Ga. Sb Quantum Dots for Intermediate Band Solar Cell - MBE growth of quantum structures for increasing efficiency. Characterization of electrical and spectral properties. Study of Intermediate band behaviour. Top Cap: 100 nm Spacer Layer Ga. Sb QD Ga. Sb Buffer: 100 nm Ga. As(n) Substrate

PROMIS A Marie Skłodowska-Curie Initial Training Network Postgraduate Research on Dilute Metamorphic Nanostructures and Metamaterials in Semiconductor Photonics Understanding efficiency limit in Single Junction CB 1. VOC = EG 2. ISC = Isc(EG) Single Junction Ideal SC limited by: • Transmission losses • Thermalization losses EG Theory: ηSJ < 31% Real: ηSJ = 25% VB Si technology

PROMIS A Marie Skłodowska-Curie Initial Training Network Postgraduate Research on Dilute Metamorphic Nanostructures and Metamaterials in Semiconductor Photonics Alternative to Single Junction: Multijunction Solar Cell Theory: ηMJ < 50% Real: ηMJ = 30% Tandem/stacked cells have produced record efficiencies by splitting the solar spectrum. - Expensive and limited to concentrator systems.

PROMIS A Marie Skłodowska-Curie Initial Training Network Postgraduate Research on Dilute Metamorphic Nanostructures and Metamaterials in Semiconductor Photonics Looking for high efficiency: Intermediate Band CB EH 1. VOC = EG 2. ISC = Isc(EG) + Isc(EH+EL) Intermediate Band Gap Ideal SC: EG IB Theory: ηSJ< ηIB=47% EL VB The Solar Energy Institute in Madrid Luque and Marti, Phys. Rev. Lett. 78 (1997) 5014 • More photons absorbed. • Less photons thermalized. IB needs to be partially filled

PROMIS A Marie Skłodowska-Curie Initial Training Network Postgraduate Research on Dilute Metamorphic Nanostructures and Metamaterials in Semiconductor Photonics MBE growth of Ga. Sb QR/QD stacks for SC

PROMIS A Marie Skłodowska-Curie Initial Training Network Postgraduate Research on Dilute Metamorphic Nanostructures and Metamaterials in Semiconductor Photonics Characterization of Ga. Sb/Ga. As QD SC VOC drops EQE(%) WL QD Ga. As Ref x 5 x 10 - Wavelength (nm) VOC drops when Ga. Sb QD are incorporated. Sub-bandgap photocurrent is detected: WL & QD.

PROMIS A Marie Skłodowska-Curie Initial Training Network Postgraduate Research on Dilute Metamorphic Nanostructures and Metamaterials in Semiconductor Photonics Intermediate Band behaviour on Ga. Sb/Ga. As SC 16 K EH Source 1+2 Source 1 EG Source 1 With a single Monochromatic light the photoresponse is limited until 0. 8 e. V (1550 nm).

PROMIS A Marie Skłodowska-Curie Initial Training Network Postgraduate Research on Dilute Metamorphic Nanostructures and Metamaterials in Semiconductor Photonics Intermediate Band behaviour on Ga. Sb/Ga. As SC 16 K EL + E H Source 1+2 Source 1 +2 EG Source 1 With a secondary source the IB is photofilled enhancing the EQE beyond 0. 6 e. V (2070 nm).

PROMIS A Marie Skłodowska-Curie Initial Training Network Postgraduate Research on Dilute Metamorphic Nanostructures and Metamaterials in Semiconductor Photonics 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.

PROMIS A Marie Skłodowska-Curie Initial Training Network Postgraduate Research on Dilute Metamorphic Nanostructures and Metamaterials in Semiconductor Photonics Summary - Solar Cells grown containing Ga. Sb QR by MBE. Ga. Sb 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.

PROMIS A Marie Skłodowska-Curie Initial Training Network Postgraduate Research on Dilute Metamorphic Nanostructures and Metamaterials in Semiconductor Photonics Skills Acquired GROWTH XRD IV PL (4 K) EQE MODELLING 2 PHOTON SET UP PROCESSING

PROMIS A Marie Skłodowska-Curie Initial Training Network Postgraduate Research on Dilute Metamorphic Nanostructures and Metamaterials in Semiconductor Photonics Outputs Talks at PROMIS Networks a) “Ga. Sb/Ga. As Quantum Dot Solar Cell” at Cadiz PROMIS Workshop, Cadiz (Spain), 4 th-6 th May 2016. b) “Two photon photocurrent in Ga. Sb/Ga. As Intermediate Band Solar Cell” at Montpellier PROMIS Workshop, Montpellier (France), 30 th Aug-3 rd Sept 2016. Posters a) “Ga. Sb/Ga. As Quantum Dot Solar Cell” at Material Science Institute, Lancaster University (Lancaster), 5 th-6 th April 2016. b) “Two photon photocurrent in Ga. Sb/Ga. As Intermediate Band Solar Cell” at MBE 16, Montpellier, 1 st-5 th Aug 2016; . c) “Ga. Sb/Ga. As Intermediate Band Solar Cell” at Photovoltaic Workshop, Imperial College (London), 15 th-16 th Sept 2016. Outreach • • Webcast on Photonics: “Solar cells”. Participation on “Day of Photonics”.

PROMIS A Marie Skłodowska-Curie Initial Training Network Postgraduate Research on Dilute Metamorphic Nanostructures and Metamaterials in Semiconductor Photonics Future aspirations - Publish high impact papers. Present talks at international conferences: • • - PVTC 2017: The Photovoltaic Technical Conference, 26 -28 April (Marseille). MBE 2018: International conference in Molecular Beam Epitaxy Sept, Sept (Shanghai). Finding a postdoc/ fellowship application/ researcher in company. Obtain a good job in academic/industry.