Homogenizing strain via reinforced lattice interaction enables efficient and stable 4T perovskite/silicon tandem solar cells

Abstract

Connecting a wide-band-gap (WBG) perovskite solar cell with a crystalline silicon (c-Si) cell enables the device to surpass the Shockley-Queisser (S-Q) limit of a single-junction solar cell. However, strain in WBG perovskites reduces the ion migration barrier and defect formation energy, severely impacting the efficiency and stability of tandem devices. Herein, we utilize benzamidinium chloride (BMCl), a molecule containing a deprotonation-resistant amidinium group, which occupies the A-site vacancy and interacts strongly with the [PbI<inf>6</inf>]4− octahedra to stabilize the crystal lattice. This strategy synergistically facilitates uniform compressive strain formation within perovskite films, increasing the ion migration barrier and defect formation energy. The optimized WBG single-junction perovskite (with a 1.67 eV band gap) and 4-terminal (4T) perovskite/Si tandem devices achieved power conversion efficiencies (PCEs) of 23.5% (22.9% certified) and 33.4%, respectively. Remarkably, the 4T tandem device showed no PCE decay after 48 days of operation under outdoor conditions, demonstrating superior real-world stability.