Improving efficiency and stability of wide-bandgap perovskite solar cells and four-terminal tandems with iso-propylammonium 2D passivator

Reducing interfacial voltage deficits in inverted wide-bandgap (WBG) perovskite solar cells (PSCs) is essential for improving the efficiency of tandem solar cells. This study introduces iso-propylammonium iodide (i-PAI) as a passivator to form a thin two-dimensional (2D) perovskite layer on three-dimensional (3D) WBG perovskite surface. The i-PAI passivation helps to decrease the phase segregation, reduce defect density at the interface, and strengthen the bonds within the perovskite layer. As a result, the i-PAI-treated WBG PSC (Eg =1.67 eV) achieved an impressive open-circuit voltage of 1.25 V and a record power conversion efficiency (PCE) of 22.4 %. Furthermore, when applied the semitransparent WBG PSC in a four-terminal (4-T) perovskite/Si tandem solar cell, the efficiency reached a PCE of 31.1 %. This study introduces a new 2D passivator for enhancing the efficiency of WBG perovskite and tandem solar cells, offering valuable references for advancing the commercial development of tandem solar technology.