Thin-film silicon-based quadruple junction solar cells approaching 20% conversion efficiency

• Multi-junction as main strategy for high efficiency thin-film silicon cells.
• Thin-film silicon quadruple junction cell studied for high potential efficiency.
• The simulated device shows 8.7 mA/cm2 matched current and efficiency close to 20%.
• Spectral overlap limits device design when pursuing current-matched condition.
• By deploying a-SiOx we designed a device with 19.8% potential efficiency.

Thin-film silicon-based solar cells are a well-established photovoltaic (PV) technology. The best reported initial and stabilized conversion efficiency is 16.3% and 13.4%, respectively. Thin-film silicon PV technology needs to achieve initial conversion efficiency approaching 20% in order to stay competitive with other PV technologies. The multi-junction approach is regarded as the main strategy for improving cells efficiency. In this contribution, we study thin-film silicon-based solar cells based on a quadruple junction device and discuss their potential for achieving a high efficiency. We carried out optical modelling of this novel device structure using state-of-the-art materials and light management techniques. We demonstrate a quadruple junction cell with simulated photo-generated current density of 8.7 mA/cm2 in current-matching condition and potential initial conversion efficiency of 19.6%. A significant spectral overlap is observed between the component cells that makes the design of the current-matched device complex. We can control the spectral overlap by employing band-gap engineering of absorber layers and design an improved current-matched quadruple junction solar cell with potential initial conversion efficiency equal to 19.8%.

Figure optionsDownload as PowerPoint slide