Researchers from Chung-Ang University (CAU), Kyoto University, Chungnam National University, Chungbuk National University and Gyeongsang National University have developed a halogen composition–independent strategy for realizing wide-bandgap (WBG) tin-based perovskite solar cells (TPSCs), by partially substituting formamidinium with dimethylammonium (DMA) in the A-site of the perovskite lattice. This substitution is said to expand the lattice, widening the bandgap from 1.63 to 1.72 eV without requiring additional bromine.
Schematic of the ST-TPSC device structure. Image credit: Small
Comprehensive structural and optical analyses revealed enhanced crystallinity, reduced strain, and improved film morphology. Furthermore, ultraviolet photoelectron spectroscopy confirmed enhanced band alignment with the hole transport layer, enabling more efficient charge extraction.
By employing a dielectric/metal/dielectric transparent electrode, semi-transparent TPSCs (ST-TPSCs) are fabricated with a PCE of 10.37% and high near-infrared transmittance, which is well-suited for tandem applications. Stacking this ST-TPSC with a narrow-bandgap TPSC yields the first four-terminal, lead-free perovskite tandem device, achieving a combined PCE of 15.02%.
These findings show that DMA incorporation effectively addresses the challenges of WBG TPSCs without relying on halogen adjustments, providing a robust pathway toward high-efficiency, eco-friendly photovoltaics and highlighting the promise of tin-based perovskites for next-generation tandem solar cells.
