Synergistic Passivation of Buried Interfaces by Rubidium Chloride and Formamidine Acetate to Improve Performance of Perovskite Solar Cells

Tin dioxide (<tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\text{SnO}_{2}$</tex>) is widely used as the electron transport layer (ETL) in efficient normal structure perovskite solar cells (PSCs). However, its surface generally adsorbed numerous hydroxyl groups which degrade the stability of devices. Here, we demonstrate that these hydroxyl groups significantly degrade the steady-state performance. To address this issue, we propose a strategy of synergistic passivation of the buried interface by rubidium chloride and formamidine acetate, which reduced terminal hydroxyl groups on the surface of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\text{SnO}_{2}$</tex> by substituting hydroxyl groups with chloride and acetate ions. After passivating the hydroxyl groups on the surface of tin dioxide using this method, the photovoltaic conversion efficiency (PCE) and stability of the PSCs were improved. As a result, the champion n-i-p device achieved a PCE of 23.43%.