Periodic Reporting for period 3 - GLISS (Gliding epitaxy for inorganic space-power sheets)
Reporting period: 2023-01-01 to 2024-06-30
In recent years the Space industry has expanded rapidly, driven by a boom in demand for satellite services. Space technologies provide ubiquitous functionalities such as communications, navigation, precision timing, meteorological data and real time imaging. These critical services are highly enabling in many aspects of modern life including agriculture, security, transport and individual mobile connectivity. The provision of satellite services in developing nations, remote locations and disaster zones, can be lifesaving in the short term and enable sustained economic development in the longer term, through the dissemination and democratisation of information. Low cost, universal access to Space services is an economic and humanitarian imperative. Restrictions of the photovoltaic system which powers satellite payloads remains a limiting factor in the provision of Space-based services and a new vision for Space power systems would enable new design paradigms, such as distributed networks of “roll-up” satellites, for unprecedented functionality. Since the start of this project, there has also been significant renewed interest in the development of Space-based solar power, extra-terrestrial solar farms which convert and beam energy to the Earth’s surface, delivering low carbon electrical power where it is needed, day or night, whatever the weather. A new Space PV technological vision is essential to meet objectives on (i) cost reduction and universal access and (ii) extended scientific capabilities. This project addresses this need with a translational program of research, ranging from fundamental design parameters to scalable fabrication methodologies.
Key objectives of this project are:
A) Fundamental performance enhancement in ultra-thin geometries including (i) development of optical structures for strong solar absorption in ultra-thin films, (ii) demonstration of performance enhancement through hot-carrier generation, (iii) demonstration of enhanced radiation resilience in these ultra-thin systems
(B) Methodologies for scalable fabrication including (i) low cost fabrication of III-V semiconductor films used for PV device fabrication, using 2D interface layers to grow releasable films, (ii) development of bonding methods to enable the integration of films with the robust mechanical support to survive harsh Space environments.
Key objectives of this project are:
A) Fundamental performance enhancement in ultra-thin geometries including (i) development of optical structures for strong solar absorption in ultra-thin films, (ii) demonstration of performance enhancement through hot-carrier generation, (iii) demonstration of enhanced radiation resilience in these ultra-thin systems
(B) Methodologies for scalable fabrication including (i) low cost fabrication of III-V semiconductor films used for PV device fabrication, using 2D interface layers to grow releasable films, (ii) development of bonding methods to enable the integration of films with the robust mechanical support to survive harsh Space environments.
In the first half of this action, several intermediate goals and corresponding research outputs towards the key objectives (A) and (B) have been achieved:
(A) Advancement of ultra-thin devices
- Light management systems for ultra-thin device geometries were simulated, providing new understanding of the design space available to maximize the absorption of solar photons in these films, including the geometry and material selection of scattering surfaces.
- Ultra-thin (80 nm) GaAs devices, orders of magnitude thinner than current commercial technologies, were fabricated using a new wafer scale patterning technique displacement Talbot lithography (DTL).
- Ground based radiation testing was performed on these ultra-thin devices and extended radiation resilience was demonstrated, indicating longer on-orbit lifetimes could be achieved with these designs.
(B) Fabrication of III-V semiconductor films using 2D interface layers
- GaAs films were grown on monolayer graphene with an underlying GaAs substrate. It was shown that wet transferred graphene produced an unwanted oxide layer at the graphene/substrate interface, degrading film quality, however this was mitigated with the controlled introduction of nanopores using an argon ion beam.
- It was shown that GaAs films grown on these damaged graphene surfaces, could still be exfoliated from the growth surface, allowing for integration and potential substrate reuse.
(A) Advancement of ultra-thin devices
- Light management systems for ultra-thin device geometries were simulated, providing new understanding of the design space available to maximize the absorption of solar photons in these films, including the geometry and material selection of scattering surfaces.
- Ultra-thin (80 nm) GaAs devices, orders of magnitude thinner than current commercial technologies, were fabricated using a new wafer scale patterning technique displacement Talbot lithography (DTL).
- Ground based radiation testing was performed on these ultra-thin devices and extended radiation resilience was demonstrated, indicating longer on-orbit lifetimes could be achieved with these designs.
(B) Fabrication of III-V semiconductor films using 2D interface layers
- GaAs films were grown on monolayer graphene with an underlying GaAs substrate. It was shown that wet transferred graphene produced an unwanted oxide layer at the graphene/substrate interface, degrading film quality, however this was mitigated with the controlled introduction of nanopores using an argon ion beam.
- It was shown that GaAs films grown on these damaged graphene surfaces, could still be exfoliated from the growth surface, allowing for integration and potential substrate reuse.
Work on this project has contributed to a number of key results beyond the state of the art:
(i) Ultra-thin GaAs solar cells with nanophotonic metal-dielectric diffraction gratings fabricated with displacement Talbot lithography (see Sayre et al., Prog Photovolt Res Appl. 2022; 30( 1): 96- 108. doi:10.1002/pip.3463)
Breakthrough elements of this work:
- Demonstration of an ultra-thin (80 nm) GaAs solar integrated nanophotonic grating that provides efficiency enhancement of 68% over an on-wafer equivalent device.
- The use of DTL for solar cell fabrication. This photolithography technique is inherently wafer-scale, allowing for high throughput, large area fabrication.
(ii) Transparent Quasi-Random Structures for Multimodal Light Trapping in Ultrathin Solar Cells with Broad Engineering Tolerance (see Camarillo Abad et al., ACS Photonics, 2022: doi: 10.1021/acsphotonics.2c00472)
Breakthrough elements of this work:
- Simulation demonstrating light trapping superiority over more widely studied nanophotonic embodiments, unlocking stronger and more abundant absorption enhancement resonances in ultra-thin solar cells.
- Pathway to solar energy conversion efficiency approaching 20% in an 80 nm GaAs absorber identified.
- Simulation demonstrating outstanding tolerance to fabrication variability, enabling light harvesting in the thinnest length-scales whilst being compatible with low-cost and scalable process methods.
(iii) Defect seeded remote epitaxy of GaAs films on graphene (see Zulqurnain et al., Nanotechnology, 2022: doi: 10.1088/1361-6528/ac8a4f)
Breakthrough elements of this work:
- Demonstration that single crystal GaAs films can be grown on a wet transferred CVD graphene monolayer, with an underlying GaAs substrate, through the controlled introduction of nanoscale defects with an argon ion beam.
- Film exfoliation, as required for integration with off-wafer device architectures and substrate reuse, is still possible even with the presence of nanoscale defects in the graphene interface monolayer.
(i) Ultra-thin GaAs solar cells with nanophotonic metal-dielectric diffraction gratings fabricated with displacement Talbot lithography (see Sayre et al., Prog Photovolt Res Appl. 2022; 30( 1): 96- 108. doi:10.1002/pip.3463)
Breakthrough elements of this work:
- Demonstration of an ultra-thin (80 nm) GaAs solar integrated nanophotonic grating that provides efficiency enhancement of 68% over an on-wafer equivalent device.
- The use of DTL for solar cell fabrication. This photolithography technique is inherently wafer-scale, allowing for high throughput, large area fabrication.
(ii) Transparent Quasi-Random Structures for Multimodal Light Trapping in Ultrathin Solar Cells with Broad Engineering Tolerance (see Camarillo Abad et al., ACS Photonics, 2022: doi: 10.1021/acsphotonics.2c00472)
Breakthrough elements of this work:
- Simulation demonstrating light trapping superiority over more widely studied nanophotonic embodiments, unlocking stronger and more abundant absorption enhancement resonances in ultra-thin solar cells.
- Pathway to solar energy conversion efficiency approaching 20% in an 80 nm GaAs absorber identified.
- Simulation demonstrating outstanding tolerance to fabrication variability, enabling light harvesting in the thinnest length-scales whilst being compatible with low-cost and scalable process methods.
(iii) Defect seeded remote epitaxy of GaAs films on graphene (see Zulqurnain et al., Nanotechnology, 2022: doi: 10.1088/1361-6528/ac8a4f)
Breakthrough elements of this work:
- Demonstration that single crystal GaAs films can be grown on a wet transferred CVD graphene monolayer, with an underlying GaAs substrate, through the controlled introduction of nanoscale defects with an argon ion beam.
- Film exfoliation, as required for integration with off-wafer device architectures and substrate reuse, is still possible even with the presence of nanoscale defects in the graphene interface monolayer.