High efficiency mesoscopic solar cells using CsPbI3 perovskite quantum dots enabled by chemical interface engineering

All-inorganic α-CsPbI3 perovskite quantum dots (QDs) are attracting high interest as solar cell absorbers due to their appealing light harvesting properties and enhanced stability due to the absence of volatile organic constituents. Moreover, ex situ synthesized QDs significantly reduce the variability of the perovskite layer deposition process. However, it is highly challenging to incorporate α-CsPbI3 QDs into mesoporous TiO2 (m-TiO2), which constitutes the best performing electron transport material in state-of-the-art perovskite solar cells. Herein, the m-TiO2 surface is engineered using an electron-rich cesium-ion containing methyl acetate solution. As one effect of this treatment, the solid-liquid interfacial tension at the TiO2 surface is reduced and the wettability is improved, facilitating the migration of the QDs into m-TiO2. As a second effect Cs+ ions passivate the QD surface and promote the charge transfer at the m-TiO2/QD interface, leading to an enhancement of the electron injection rate by ...