• Meneghini, Carlo
• Saha, Rafikul Ali
• Steele, Julian A.
• Ariza, Rocío
• Roeffaers, Maarten B. J.
• Wang, Hongxia
• Solano, Eduardo
• Hoang, Minh Tam
• Angelis, Francesco De
• Mali, Sawanta S.
• Wang, Lianzhou
• Detavernier, Christophe
• Degutis, Giedrius
• Garnett, Erik C.
• Filez, Matthias
• Orlov, Nikolai
• Chiu, Wei Hsun
• Chen, Peng

Abstract

<p>The desire to commercialize perovskite solar cells continues to mount, motivating the development of scalable production. Evaluations of the impact of open-air processing have revealed a variety of physical changes in the fabricated devices─with few changes having the capacity to be functionalized. Here, we highlight the beneficial role of ambient oxygen during the open-air thermal processing of metastable γ-CsPbI₃-based perovskite thin films and devices. Physiochemical-sensitive probes elucidate oxygen intercalation and the formation of Pb-O bonds in the CsPbI₃ crystal, entering via iodine vacancies at the surface, creating superoxide (O₂^-) through electron transfer reactions with molecular oxygen, which drives the formation of a zero-dimensional Cs₄PbI₆ capping layer during annealing (&gt;330 °C). The chemical conversion permanently alters the film structure, helping to shield the subsurface perovskite from moisture and introduces lattice anchoring sites, stabilizing otherwise unstable γ-CsPbI₃ films. This functional modification is demonstrated in γ-CsPbI₂Br perovskite solar cells, boosting the operational stability and photoconversion efficiency of champion devices from 12.7 to 15.4% when annealed in dry air. Such findings prompt a reconsideration of glovebox-based perovskite solar cell research and establish a scenario where device fabrication can in fact greatly benefit from ambient oxygen.</p>

Topics

• perovskite
• impedance spectroscopy
• surface
• thin film
• Oxygen
• annealing