Silicon Surfaces and Interfaces (PP1.2)
PP1.2 Silicon Materials
The surfaces and interfaces work package aims to develop innovative thin film technologies that can be used as building blocks at the surfaces/interfaces of future silicon solar cells to enable higher efficiency and lower levelized cost of energy (LCOE).
The ITRPV projection of continual reduction in $/Wp and LCOE of silicon photovoltaics is increasingly enabled by the innovative use of nanoscale thin films in silicon solar cells. The recent transition from Al-BSF to PERC solar cells involved introducing a locally opened nanoscale dielectric thin-film stack at the rear. of the cell. Many of the emerging high-efficiency silicon solar architectures include more thin, functional films. The best results are typically obtained when they can fulfill multiple functions during fabrication or in the final device structure.
At the core of the research strategy is fundamental materials science: the discovery of novel materials, novel combinations, and tuning of known materials to enhance functionality or extend their fundamental properties to include new functionalities. Each functionality, either alone or in combination with one or two others, provides a potential application of the thin film, creating a building block which can be used to enhance existing devices or as a foundation upon which novel device architectures can be built.
A prime example of such a multifunctional thin-film structure is the doped polysilicon on tunnel-oxide stack, which simultaneously provides excellent surface passivation, carrier selectivity, lateral conductivity, and gettering properties. Its versatility enabled the TOPCon Si architecture, a rapidly developing technology projected to be utilized in 30% of all PV modules by 2030 (ITRPV, 2021).
Another example is the silicon heterojunction solar cell structure, in which a ~5 nm doped amorphous silicon film is deposited on a ~5 nm intrinsic amorphous silicon film, resulting in a high-quality passivating contact. An alternative variation involves the incorporation of metal compound thin films in the place of doped silicon layers, which with further development may reduce optical losses.
To date, all silicon solar cells with efficiencies above 25% have utilised using either silicon heterojunction or doped polysilicon on tunnel-oxide contacts. However, there is still ample room for further improvement, particularly in relation to the industrialization of these kinds of solar cells.
ANU, UNSW and UoM are collectively leaders in this field of research and are well equipped with world-class laboratories, which have recently been substantially upgraded with ~$5+million funding from ACAP Infrastructure Funding towards expanding capabilities in materials deposition.
These newly upgraded facilities will provide globally competitive capabilities for developing novel materials and tuning their properties, with a wide range of potential synergistic combinations.
Investigators: Chern Fong (ANU), Lachlan Black (ANU), Bram Hoex (UNSW), Brett Hallam (UNSW), Ziv Hameiri (UNSW), James Bullock (UoM), Daniel Macdonald (ANU)
The expected outcome of surfaces and interfaces work package is the discovery, development, and demonstration of the next generation of multifunctional thin film technologies, which will enable a significant leap in device performance, reduction in manufacturing costs, and will unlock a new generation of device designs for the single and tandem silicon cell technologies that are needed to enable manufacturing of silicon cells with efficiencies of 25% and tandem cells targeting 30% efficiencies. Novel contact technologies developed within this package will be demonstrated in prototype devices over 24% efficiency, and demonstration of recombination junction technologies in bottom tandem devices with over 720mV implied-Voc.
PP1.2.1 Doped tunnel-oxide polysilicon
PP1.2.2 Advanced Heterocontacts
PP1.2.3 Advanced Dielectrics
PP1.2.4 Recombination Junction