Researchers from Karlsruhe Institute of Technology (KIT), Sun Yat-sen University, University of Cambridge, Eastern Institute of Technology and Hanwha Q CELLS GmbH have reported a breakthrough in perovskite/silicon tandem solar cell design that addresses one of the field’s most persistent challenges - interfacial non-radiative recombination.
The recent study introduces a bilayer passivation strategy that enhances both the efficiency and stability of tandem solar cells by precisely engineering the interface between the perovskite absorber and the electron transport layer (ETL). This approach combines an ultrathin aluminum oxide (AlOx) layer, deposited via atomic layer deposition (ALD), with a propane-1,3-diammonium iodide (PDAI₂) layer. Together, these layers fine-tune the perovskite’s energy level alignment, reduce defect densities, and effectively suppress energy losses at the interface.
At the nanoscale, ALD-AlOx forms a homogeneous coating over perovskite grains while creating island-like structures at grain boundaries - features that improve local contact and facilitate moderate n-type doping when combined with PDAI₂. This structure simultaneously serves as an ion diffusion barrier and enhances charge extraction and transport, optimizing both device performance and durability.
As a result, the team’s monolithic perovskite/silicon tandem solar cells achieved a record power conversion efficiency (PCE) of 31.6%, with a certified PCE of 30.8% using industrial Q.ANTUM silicon bottom cells from Q CELLS. The devices maintained 95% of their initial efficiency after 1,000 hours of continuous operation under maximum power point tracking—demonstrating exceptional long-term stability.
Beyond achieving impressive performance, this work establishes a research framework for systematically analyzing energy losses and guiding the design of effective passivation strategies for tandem photovoltaics. The AlOx/PDAI₂ bilayer approach provides a scalable pathway for addressing interfacial defects, balancing ionic migration, and enhancing both efficiency and operational robustness in next-generation perovskite/silicon tandem devices.
