Acetylacetone modulated TiO₂ nanoparticles for low-temperature solution processable perovskite solar cell

TiO₂ has been widely adopted as an electron transport layer during the fabrication of efficient metal halide perovskite solar cells (MHP-SCs). In this study, we prepared acetylacetone (Acac)-modulated TiO₂ nanoparticles (NPs) suitable for low-temperature solution processing via the sol-gel method. Acac coordinates with TiO₂ NPs and preferably passivates surface trap states which are detrimental to photovoltaic performance. Moreover, the Acac-TiO₂ NPs establish a favorable band alignment for charge extraction by donating the lone pair electron. As a result, Acac-TiO₂ NPs based MHP-SCs exhibit an outstanding power conversion efficiency (PCE) of 21.20% attributed to facilitated charge extraction and reduced defect density. Furthermore, by implementing low-temperature solution-processable Acac-TiO₂ NPs, we successfully demonstrated a remarkable PCE of 18.01% along with excellent mechanical stability, retaining 74.5% and 67.1% PCE after 5000 bending cycles in outward and inward directions from Acac-TiO₂ NPs based MHP-SCs on a flexible substrate.