• Moonie, Paul
• Yang, Yang
• Pham, Ngoc Duy
• Martens, Wayde
• Tulloch, Gavin
• Koplick, Andrew
• Wang, Hongxia
• Chiu, Wei Hsun
• Yu, Yongyue

Abstract

<jats:title>Abstract</jats:title><jats:p>The facile synthesis and beneficial properties of tin oxide have driven the development of efficient planar perovskite solar cells (PSCs). To increase the PSC performance, alkali salts are used to treat the SnO<jats:sub>2</jats:sub> surface to minimize the defect states. However, the underlying mechanism of alkali cations' role in the PSCs needs further exploration. Herein the effect of alkali fluoride salts (KF, RbF, and CsF) on the properties of SnO<jats:sub>2</jats:sub> and PSC performance is investigated. The results show different alkali have significant roles depending on their nature. Larger cations Cs<jats:sup>+</jats:sup> preferably locate at the SnO<jats:sub>2</jats:sub> film surface to passivate surface defects and enhance conductivity, while smaller cations like Rb<jats:sup>+</jats:sup> or K<jats:sup>+</jats:sup> cations tend to diffuse into the perovskite layer to reduce trap density of the material. The former effect leads to enhanced fill factor while the latter effect increases the open circuit voltage of the device. It is then demonstrated that a dual cation post‐treatment of the SnO<jats:sub>2</jats:sub> layer with RbF and CsF achieves PSC with a significantly higher power conversion efficiency (PCE) of 21.66% compared to pristine PSC with a PCE of 19.71%. This highlights the significance of defect engineering of SnO<jats:sub>2</jats:sub> using selective multiple alkali treatment to improve PSC performance.</jats:p>

Topics

• density
• perovskite
• impedance spectroscopy
• surface
• defect
• tin
• power conversion efficiency
• Alkali metal