Atomic Layer Deposition-Free Monolithic Perovskite/Perovskite/Silicon Triple-Junction Solar Cells

Perovskite/perovskite/silicon (PVSK/PVSK/Si) triple-junction (3J) tandem solar cells may exhibit higher efficiencies than their PVSK/Si double-junction (2J) counterparts; however, their best efficiency is still significantly lower due to the chemical degradation of the PVSK middle cell by solvents and the poor performance of the PVSK top cell. This paper reports the use of a highly volatile solvent mixture to prevent solvent penetration across the recombination layer between two PVSK subcells and to demonstrate efficient PVSK/PVSK tandems even without atomic layer deposition protection layers. The photovoltaic performance of the PVSK top cell, with a bandgap energy of 1.96 eV, can be improved from 6.4% to 13.9% by adding urea, mainly due to the enhanced crystallinity and light-absorbing capability. With the aid of the new volatile solvent and the urea additive, the final monolithic PVSK/PVSK/Si 3J tandems exhibited a record-high conversion efficiency of 22.23%.