Nonspiro, Fluorene‐Based, Amorphous Hole Transporting Materials for Efficient and Stable Perovskite Solar Cells.

Abstract: Novel nonspiro, fluorene‐based, small‐molecule hole transporting materials (HTMs) <bold>V1050</bold> and <bold>V1061</bold> are designed and synthesized using a facile three‐step synthetic route. The synthesized compounds exhibit amorphous nature with a high glass transition temperature, a good solubility, and decent thermal stability. The planar perovskite solar cells (PSCs) employing <bold>V1050</bold> generated an excellent power conversion efficiency of 18.3%, which is comparable to 18.9% obtained with the state‐of‐the‐art Spiro‐OMeTAD. Importantly, the devices based on <bold>V1050</bold> and <bold>V1061</bold> show better stability compared to devices based on Spiro‐OMeTAD when aged without any encapsulation under uncontrolled humidity conditions (relative humidity around 60%) in the dark and under continuous full sun illumination. [ABSTRACT FROM AUTHOR]