Binary Cations Minimize Energy Loss in the Wide Bandgap Perovskite Towards Efficient All-Perovskite Tandem Solar Cells

Abstract

Perovskite-based tandem solar cells, known for their exceptional performance and cost-effective fabrication, are at the forefront of photovoltaic technologies. This study addresses key challenges in enhancing the efficiency and stability of these tandem devices, focusing on the front wide-bandgap perovskite sub-cell. The surface treatment of a 1.80 eV perovskite with binary cations, specifically guanidinium bromide and 4-fluorophenylammonium iodide, proves instrumental in reducing defect densities and mitigating interfacial energy barriers. This treatment significantly suppresses non-radiative recombination and transport losses, resulting in a remarkable open circuit voltage and fill factor (VOC × FF) product of 1.061 V and a notable power conversion efficiency (PCE) of 19.0%. Reproducibility is underscored by consistent results across different laboratories. Furthermore, integration with a tin-based narrow-bandgap perovskite yields an all-perovskite tandem device boasting a cutting-edge PCE of 27.2%. This comprehensive exploration of spacer cations’ pivotal role in perovskite surface treatment advances the technology for commercialization.

Keywords: all-perovskite tandem solar cell, wide bandgap perovskite, energy loss, non-radiative recombination, energy level alignment, reproducibility