A Facile Surface Passivation for Thermally Stable Planar Perovskite Solar Cells by Using a Novel IDTT-Based Small Molecule Additive

Perovskite solar cells (PSCs) have been highlighted as next-generation solar cells owing to their fascinating optoelectronic properties and solution processability. However, defects in PSCs, which could lower effciency and stability, are still not completely resolved. To solve aforementioned issues, a novel indacenodithieno[3,2-b]thiophene-based small molecule (SM) additive (IDTT-ThCz) is developed. In particular, the IDTT-ThCz, which can perform a surface passivation, is introduced into the perovskite layer via antisolvent treatment and suppresses perovskite defects. Furthermore, the introduction of this molecule not only facilitates the charge extraction capability, but also delays perovskite degradation. As a result, the IDTT-ThCz-treated PSCs exhibits a power conversion effciency (PCE) of 22.5% and retains 95% of its initial PCE after 500 h storage under thermal condition (85°C).