Four-terminal perovskite/c-Si tandem PV technology

Two factors have coincided to stimulate the recent spur in interest for hybrid tandem PV technology based on crystalline silicon – the fact that balance-of-system (BOS) costs are increasingly dominating turnkey system costs, which strengthens the effect of high efficiency in reducing Wp costs, and the discovery of perovskite solar cells as a promising low-cost wide-band-gap partner for crystalline silicon (c-Si). This paper presents the progress and analysis of four-terminal (4T) perovskite/c-Si tandem technology at ECN part of TNO, with perovskite technology development carried out within the Solliance research organization. Tandem cell optimization and optical loss analysis are presented, with the combination of high efficiency and high near-infrared (NIR) transmittance of the perovskite cell resulting in an experimental tandem efficiency of 26.3%. An outlook is offered for loss reduction and efficiency increase. Upscaling and interconnection of the perovskite cell are crucial aspects for industrialization, and the status at Solliance is briefly described. High-end c-Si bottom cells are then compared with mainstream industrial cells; how industrial PERC and nPERT cells can be optimized for tandem application is described, as well as even making them suitable for two-terminal tandem application, through the application of polysilicon (polySi) passivated contacts. Finally, this paper looks at the cost of tandem versus single-junction (SJ) c-Si systems, and shows that the recent literature on perovskite module manufacturing cost is consistent with a potential cost advantage of tandem devices.