Photovoltaics

Two types of approaches are followed in this field: (i) developing new direct bandgap materials having a high absorption coefficient at the maximum wavelength of the solar spectrum for extremely thin absorber solar cells, and (ii) studying new concepts such as type II band-gap alignment and core/shell structures to optimize photovoltaics conversion, especially to improve the separation of the photo-generated e-h pairs and hinder radiative losses.

The motivation for the study of Cu2ZnSn(S,Se)4 alloy is to propose an alternative to CdTe and Cu(In,Ga)S2, which are composed of elements not abundant in the earth crust (Te and In) or toxic (Cd). So far, the development of Cu2ZnSn(S,Se)4 layers was limited to polycrystalline films with micrometer size domains when they are grown on molybdenum coated soda lime glass (usual substrate for these PV cells). In closed collaboration with CEA/LITEN, we achieved such cells with efficiency up to 7%. The Cu2ZnSn(S,Se)4 layers suffer from the presence of many crystallographic defects that are still difficult to suppress (grain boundaries, secondary phases, stoichiometry, points defects). To elucidate the role of all these defects, we started a study of monocrystalline Cu2ZnSn(S,Se)4 thin films grown by MBE in order to establish experimentally the intrinsic properties of this new material.

We have studied CdSe/ZnTe superlattices, to evaluate a new concept of solar cells. This concept aims at optimizing both, the band-gap of the absorber to fit the solar spectrum (1.4 eV), and the carrier collection thanks to a peculiar band alignment at the interface of some semiconductors: the so-called type II band structure. The idea, to go beyond the simple charge separation by a pn junction, can be summarized as follows: the sun absorber is a short period CdSe/ZnTe superlattice and the two contact materials are respectively CdSe, to collect electrons, and ZnTe, to collect holes. Conversely CdSe is a high barrier for holes and ZnTe is a high barrier for electrons. In other words, this solar absorber is intrinsically fitted with optimized contacts. For example, we have grown by MBE a 5ML/7ML superlattice, which exhibits photoluminescence at 1.45 eV and a PL decay time of a few ns, showing that the superlattice behaves as an ordered alloy. Spontaneous dissociation of e-h pairs by a piezoelectric field was also studied in core/shell nanowires such as GaAs/AlGaAs, which are grown along a polar direction.

Quantum Electronic Circuits Alps - QuantECA

Quantum Electronic Circuits Alps - QuantECA

Quantum phenomena in electronic circuits : from model systems to large scale integration.
Helium : from fundamental to applications - HELFA

Helium : from fundamental to applications - HELFA

Helium as model system, hydrodynamic and turbulence, space and astrophysics, instrumentation and cryogenic development, kinetic inductance detectors.
Magnetism and Superconductivity - MagSup

Magnetism and Superconductivity - MagSup

Team Magnetism and Superconductivity at Institut NEEL - Systems involving charge, spin or lattice degrees of freedom.
Optics and materials - OPTIMA

Optics and materials - OPTIMA

a complete chain of competences that goes from the design and elaboration of new materials to the study of nonlinear optical properties and plasmonics
Materials, Radiations, Structure - MRS

Materials, Radiations, Structure - MRS

Understanding of the physico-chemical properties of complex materials based on the precise description of their structure
Micro and NanoMagnetism - MNM

Micro and NanoMagnetism - MNM

Complementary expertise in fabrication, characterisation, and simulations for studies in nanomagnetism with applications in spin electronics and micro-systems
Quantum Nano-Electronics and Spectroscopy - QNES

Quantum Nano-Electronics and Spectroscopy - QNES

Electron transport and local spectroscopy of quantum structures
Nano-Optics and Forces - NOF

Nano-Optics and Forces - NOF

Nano - optics and forces
Nanophysics and Semiconductors - NPSC

Nanophysics and Semiconductors - NPSC

Growth of III-V and II-VI semiconductor nanostructures and their physics in search of new functions for potential applications.
Wide bandgap semiconductors - SC2G

Wide bandgap semiconductors - SC2G

Physics of diamond and other wide bandgap semiconductors towards applications in electronics and biotechnologies
Surfaces, Interfaces and Nanostructures - SIN

Surfaces, Interfaces and Nanostructures - SIN

Experimental and theoretical studies of low dimensional systems
Hybrid systems at low dimensions - HYBRID

Hybrid systems at low dimensions - HYBRID

Electronic, optical, vibrational, mechanical properties, as well as their interplay at the nanoscale, of novel hybrid systems (nanotubes, graphene, two-dimensional and functionalized materials) which are developed by the group .
Condensed Matter Theory - TMC

Condensed Matter Theory - TMC

Theoretical research related to quantum materials and first-principles theory. >> read more
Thermodynamics and Biophysics of small systems - TPS

Thermodynamics and Biophysics of small systems - TPS

Ultra-sensitive instrumentation for electrical and thermal measurements: from biophysics to low temperature condensed matter physics.
Theory of Quantum Circuits - ThQC

Theory of Quantum Circuits - ThQC

Theoretical studies of electronic transport in nanometer-scale devices showing remarkable quantum effects.
Ultra-low temperatures - UBT

Ultra-low temperatures - UBT

Quantum physics at the ultra-low temperature frontier.
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