Jonathan Grandidier

Light Absorption Enhancement in Thin‐Film Solar Cells Using Whispering Gallery Modes in Dielectric Nanospheres

Freely propagating sunlight can be diffractively coupled and transformed into several guided whispering gallery modes within an array of wavelength scale dielectric spheres. Incident optical power is then transferred to the thin-film cell by leaky mode coupling into a thin solar cell absorber layer and significantly enhances its efficiency by increasing the fraction of incident light absorbed.

Efficient Coupling between Dielectric-Loaded Plasmonic and Silicon Photonic Waveguides

The realization of practical on-chip plasmonic devices will require efficient coupling of light into and out of surface plasmon waveguides over short length scales. In this letter, we report on low insertion loss for polymer-on-gold dielectric-loaded plasmonic waveguides end-coupled to silicon-on-insulator waveguides with a coupling efficiency of 79 ± 2% per transition at telecommunication wavelengths. Propagation loss is determined independently of insertion loss by measuring the transmission through plasmonic waveguides of varying length, and we find a characteristic surface-plasmon propagation length of 51 ± 4 μm at a free-space wavelength of λ = 1550 nm. We also demonstrate efficient coupling to whispering-gallery modes in plasmonic ring resonators with an average bending-loss-limited quality factor of 180 ± 8.

Gallium Arsenide Solar Cell Absorption Enhancement Using Whispering Gallery Modes of Dielectric Nanospheres

Based on a perfectly flat gallium arsenide solar cell, we show that it is possible to modify the flow of light and enhance the absorption without modifying the active material structure or degrading its electrical properties. The sunlight couples into confined resonant modes formed by a periodic arrangement of dielectric nanospheres above the solar cell. The in coupling element is lossless and, thus, has the advantage that no energy is lost within the dielectric nanospheres. This stored energy is absorbed by the underlying active material which directly contributes to the photocurrent enhancement of the solar cell.

Simulations of solar cell absorption enhancement using resonant modes of a nanosphere array

We propose an approach for enhancing the absorption of thin-film amorphous silicon solar cells using periodic arrangements of resonant dielectric nanospheres deposited as a continuous film on top of a thin planar cell. We numerically demonstrate this enhancement using three dimensional (3D) full field, finite difference time domain simulations and 3D finite element device physics simulations of a nanosphere array above a thin-film amorphous silicon solar cell structure featuring back reflector and anti-reflection coating. In addition, we use the full field finite difference time domain results as input to finite element device physics simulations to demonstrate that the enhanced absorption contributes to the current extracted from the device. We study the influence of a multi-sized array of spheres, compare spheres and domes, and propose an analytical model based on the temporal coupled mode theory.

Scanning near-field optical microscopy on dense random assemblies of metal nanoparticles

Plasmonic absorption enhancement by metal nanoparticles strongly relies on the local electric field distributions generated by the nanoparticles. Therefore, here we study random assemblies of metal nanoparticles as they are widely considered for solar cell application with scanning near-field optical microscopy. A collective scattering behavior is observed despite a resolution on the particle size. We find variations in scattering intensity on a length scale several times larger than in the topography. FDTD (finite-difference time domain) simulations show the impact of irregularities and size variations on the scattering behavior. An understanding of the plasmonic scattering behavior at the nanometer scale will support the successful application of nanoparticles for absorption enhancement in thin-film solar cells.

TEMPERATURE-STAGED THERMAL ENERGY STORAGE ENABLING LOW THERMAL EXERGY LOSS REFLUX BOILING IN FULL SPECTRUM SOLAR ENERGY SYSTEMS

The efficiency of solar power collection is increased by adding a thermal energy storage stage to a sunlight concentrator and thermodynamic power generator system. The thermal energy storage includes tubes or capsules made of a phase change material that stores thermal energy in different temperature stages through a working fluid. The stored thermal energy is directed to the thermodynamic generator during off-sun periods.

Configuration optimization of a nanosphere array on top of a thin film solar cell

Resonant dielectric structures placed on top of a solar cell can enhance light absorption and therefore increase its efficiency. Freely propagating sunlight diffractively couples into the resonant modes of a low loss sphere array. We numerically demonstrate this enhancement using 3D full field finite difference time domain simulations. The coupled energy is then transferred into the active layer underneath and significantly contributes to increase the calculated photocurrent of the solar cell. On a typical thin film amorphous silicon solar cell, a parametric analysis is done. For a hexagonally close packed sphere configuration, we vary the size of the spheres as well as the type of material used. Finally, we study a configuration where high index spheres are embedded in a lower index polymer. This last configuration has the advantage that it can easily be integrated upon solar cell fabrication.

Full spectrum hybrid photovoltaics and thermal engine utilizing high concentration solar energy

We describe a Hybrid full spectrum solar system (FSSS) that utilizes the full spectrum available from the sun. It is designed to convert the full solar spectrum into useful electrical energy by using both photovoltaics energy conversion and thermal energy conversion combined with thermal energy storage (TES) in order to operate around-the-clock even when solar energy is not available. It is composed of a parabolic dish concentrator and a hybrid high temperature photovoltaics and thermal engine. The target efficiency of the overall system is over 35% with the AM1.5D solar spectrum as a power input.

Absorption enhancing and passivating non-planar thin-film device architectures for copper indium gallium selenide photovoltaics

The sub-micrometer absorber regime is currently being explored to reduce materials usage and deposition time while simultaneously increasing device voltages due to increased generated carrier concentration. In order to realize these benefits, the absorption of photons must be maintained or even increased while avoiding detrimental recombination. Reported here are optoelectronic simulations that highlight photon and generated carrier management opportunities for improvement of thin film Cu(InxGa1-x)Se2 (CIGSe) device performance. Structures that could be created via either self-assembly, patterning by nanoimprint lithography, or a combination of both are predicted to significantly increase short circuit current density and open circuit voltage simultaneously.

Solar cell measurements at high temperature

Photovoltaic (PV) power technology is in principle capable of operating in a high temperature environment, but little work has been done to understand how to adapt currently available device and system technologies for extreme conditions. The objective of this work is to look at the performance of a multi-junction concentrator solar cell operating at high temperature and to find promising approaches to increase the efficiency of a solar cell under extreme conditions.