Tuned Bottom Silicon Devices (PP3.4)
PP3.4: Tuned Bottom Silicon Devices
The aim of this work package is the demonstration of highly tuned bottom silicon devices and development of enabling technologies, guided by a detailed technology roadmap based on current technology projections and state-of-the-art device simulations.
Tandem PV with a bottom silicon cell is projected to enter the PV market within the next 5 years and occupy a ~5% market share within the next 10 years (ITRPV, 2021). The suitability of silicon devices as the bottom cell is driven by both economic and technical factors. Silicon devices are a highly matured PV product with over 90% of the PV market, owing to its potential for high efficiencies 25-27%, low-cost fabrication processes ($/Wp), and low LCOE.
Silicon as a bottom cell with an energy band gap of ~1.12eV is capable of effectively absorbing and converting long wavelength light up to 1000nm with near 100% internal quantum efficieny (IQE), enabling a highly synergistic combination with the higher bandgap materials in emerging PV materials such as perovskites, GaAs, CZTS and various OPV materials.
Two-terminal tandems with silicon as the bottom cell have been demonstrated to achieve very high efficiencies, achieving 32.9% with GaAs/silicon, and 29.2% Perovskite/silicon tandems and showing rapid progression in recent years. Development of such ultra-high efficiency modules is particularly advantageous to Australia where high balance-of-system costs for residential PV installations represents >50% of the total PV market.
A vast range of research, development, integration, commercialisation and demonstration activities are needed to realise a commercial silicon-tandem product within the next decade. This work package will address the most pressing issues relating to design and development of the optimal bottom silicon cell structure incorporating passivated contacts, optimal optical light trapping schemes, and advanced interface contact technologies.