Rebecca Saive - Academia.edu (original) (raw)

Papers by Rebecca Saive

Advanced Optical Materials, 2016

Communication between grid finger resistance and the sheet resistance and transmission losses of ... more Communication between grid finger resistance and the sheet resistance and transmission losses of the transparent conducting oxide (TCO)/ amorphous silicon structures coating the cell front surface. [24] In this paper, we describe a new front contact design principle that overcomes both shadowing losses and parasitic absorption without reducing the conductivity. By redirecting the scattered light incident on the front contact to the solar cell active absorber layer surface, micrometer-scale triangular cross-section grid fingers can perform as effectively transparent and highly conductive front contacts. Previously, researchers have designed light harvesting strings that serve to obliquely reflect light, which is then redirected into the cell by total internal reflection from the encapsulation layers. [16] By contrast our front contact design does not require total internal reflection at the encapsulation layer. Furthermore in our design, the contact fingers are micrometer sized and can be placed very close together such that a TCO with reduced thickness can be used—and in some cases the TCO layer might possibly be omitted completely. We demonstrate with simulations and experimental results that designs utilizing effectively transparent triangular cross-section grid fingers rather than conventional front contacts have the potential to provide 99.86% optical transparency while ensuring efficient lateral transport corresponding to a sheet resistance of 4.8 Ω sq −1 due to their close spacing of only 40 μm. Thus effectively transparent contacts have potential as replacements for both the front grid and TCO layer used, e.g., in HIT solar cells. While related schemes for contacts were envisioned early in the development of photovoltaics technology, [25] they have not found application in current photovoltaic technology, which is increasingly dominated by high efficiency silicon photovol-taics. Moreover, the effectively transparent front contact design is conceptually quite general and applicable to almost any other front-contacted solar cell or optoelectronic device. For example, we obtained similar experimental results when applying our structures to InGaP-based solar cells. Figure 1a,b shows the steady-state electric field magnitude distribution of a freestanding triangular contact and a flat contact , respectively, with 550 nm monochromatic plane wave illumination normally incident at the top of the simulation cell. For planar grid fingers, part of the incident light is reflected back toward the incidence direction, as is apparent from the high electric field density above the contact plane. By contrast, the triangular cross-section grid finger does not exhibit a similar back reflection, as indicated by the lack of an increased electric field density in the incidence direction. However an enhancement of the electric field is seen in the forward scattering direction, behind the contact, explaining its effective transparency.

physica status solidi (RRL) - Rapid Research Letters, 2015

Physical Review X, 2012

We investigate single photon generation from individual self-assembled InGaAs quantum dots couple... more We investigate single photon generation from individual self-assembled InGaAs quantum dots coupled to the guided optical mode of a GaAs photonic crystal waveguide. By performing confocal microscopy measurements on single dots positioned within the waveguide, we locate their positions with a precision better than 0.5 µm. Time-resolved photoluminescence and photon autocorrelation measurements are used to prove the single photon character of the emission into the propagating waveguide mode. The results obtained demonstrate that such nanostructures can be used to realize an on-chip, highly directed single photon source with single mode spontaneous emision coupling efficiencies in excess of βΓ ∼ 85 % and the potential to reach maximum emission rates > 1 GHz.

AIP Advances, 2013

ABSTRACT

Organic Electronics, 2013

ABSTRACT

Journal of Applied Physics, 2012

The authors investigate the spontaneous emission dynamics of selfassembled InGaAs quantum dots em... more The authors investigate the spontaneous emission dynamics of selfassembled InGaAs quantum dots embedded in GaAs photonic crystal waveguides. For an ensemble of dots coupled to guided modes in the waveguide we report spatially, spectrally, and time-resolved photoluminescence measurements, detecting normal to the plane of the photonic crystal. For quantum dots emitting in resonance with the waveguide mode, a ∼ 21× enhancement of photoluminescence intensity is observed as compared to dots in the unprocessed region of the wafer. This enhancement can be traced back to the Purcell enhanced emission of quantum dots into leaky and guided modes of the waveguide with moderate Purcell factors up to ∼ 4×. Emission into guided modes is shown to be efficiently scattered out of the waveguide within a few microns, contributing to the out-of-plane emission and allowing the use of photonic crystal waveguides as broadband, efficiency-enhancing structures for surface-emitting diodes or single photon sources.

Applied Physics Letters, 2013

Advanced Functional Materials, 2013

2015 IEEE 42nd Photovoltaic Specialist Conference (PVSC), 2015

Advanced Optical Materials, 2016

Communication between grid finger resistance and the sheet resistance and transmission losses of ... more Communication between grid finger resistance and the sheet resistance and transmission losses of the transparent conducting oxide (TCO)/ amorphous silicon structures coating the cell front surface. [24] In this paper, we describe a new front contact design principle that overcomes both shadowing losses and parasitic absorption without reducing the conductivity. By redirecting the scattered light incident on the front contact to the solar cell active absorber layer surface, micrometer-scale triangular cross-section grid fingers can perform as effectively transparent and highly conductive front contacts. Previously, researchers have designed light harvesting strings that serve to obliquely reflect light, which is then redirected into the cell by total internal reflection from the encapsulation layers. [16] By contrast our front contact design does not require total internal reflection at the encapsulation layer. Furthermore in our design, the contact fingers are micrometer sized and can be placed very close together such that a TCO with reduced thickness can be used—and in some cases the TCO layer might possibly be omitted completely. We demonstrate with simulations and experimental results that designs utilizing effectively transparent triangular cross-section grid fingers rather than conventional front contacts have the potential to provide 99.86% optical transparency while ensuring efficient lateral transport corresponding to a sheet resistance of 4.8 Ω sq −1 due to their close spacing of only 40 μm. Thus effectively transparent contacts have potential as replacements for both the front grid and TCO layer used, e.g., in HIT solar cells. While related schemes for contacts were envisioned early in the development of photovoltaics technology, [25] they have not found application in current photovoltaic technology, which is increasingly dominated by high efficiency silicon photovol-taics. Moreover, the effectively transparent front contact design is conceptually quite general and applicable to almost any other front-contacted solar cell or optoelectronic device. For example, we obtained similar experimental results when applying our structures to InGaP-based solar cells. Figure 1a,b shows the steady-state electric field magnitude distribution of a freestanding triangular contact and a flat contact , respectively, with 550 nm monochromatic plane wave illumination normally incident at the top of the simulation cell. For planar grid fingers, part of the incident light is reflected back toward the incidence direction, as is apparent from the high electric field density above the contact plane. By contrast, the triangular cross-section grid finger does not exhibit a similar back reflection, as indicated by the lack of an increased electric field density in the incidence direction. However an enhancement of the electric field is seen in the forward scattering direction, behind the contact, explaining its effective transparency.

physica status solidi (RRL) - Rapid Research Letters, 2015

Physical Review X, 2012

We investigate single photon generation from individual self-assembled InGaAs quantum dots couple... more We investigate single photon generation from individual self-assembled InGaAs quantum dots coupled to the guided optical mode of a GaAs photonic crystal waveguide. By performing confocal microscopy measurements on single dots positioned within the waveguide, we locate their positions with a precision better than 0.5 µm. Time-resolved photoluminescence and photon autocorrelation measurements are used to prove the single photon character of the emission into the propagating waveguide mode. The results obtained demonstrate that such nanostructures can be used to realize an on-chip, highly directed single photon source with single mode spontaneous emision coupling efficiencies in excess of βΓ ∼ 85 % and the potential to reach maximum emission rates > 1 GHz.

AIP Advances, 2013

ABSTRACT

Organic Electronics, 2013

ABSTRACT

Journal of Applied Physics, 2012

The authors investigate the spontaneous emission dynamics of selfassembled InGaAs quantum dots em... more The authors investigate the spontaneous emission dynamics of selfassembled InGaAs quantum dots embedded in GaAs photonic crystal waveguides. For an ensemble of dots coupled to guided modes in the waveguide we report spatially, spectrally, and time-resolved photoluminescence measurements, detecting normal to the plane of the photonic crystal. For quantum dots emitting in resonance with the waveguide mode, a ∼ 21× enhancement of photoluminescence intensity is observed as compared to dots in the unprocessed region of the wafer. This enhancement can be traced back to the Purcell enhanced emission of quantum dots into leaky and guided modes of the waveguide with moderate Purcell factors up to ∼ 4×. Emission into guided modes is shown to be efficiently scattered out of the waveguide within a few microns, contributing to the out-of-plane emission and allowing the use of photonic crystal waveguides as broadband, efficiency-enhancing structures for surface-emitting diodes or single photon sources.

Applied Physics Letters, 2013

Advanced Functional Materials, 2013

2015 IEEE 42nd Photovoltaic Specialist Conference (PVSC), 2015