Surface Ligand Management for Stable FAPbI3 Perovskite Quantum Dot Solar Cells

In contrast to conventional colloidal quantum dots (CQDs), management of insulating ligands on perovskite CQDs is challenging because their ionic bonds are highly vulnerable to polar solvents. Consequently, there have been only a few examples of perovskite CQD solar cells incorporating relatively robust inorganic perovskite of which optoelectronic properties are not ideal for photovoltaic devices. Here, we report efficient and stable CQD solar cells based on formamidinium lead triiodide (FAPbI3) CQDs realized by rational surface regulation. Tailoring polarity of antisolvents for the post-synthetic process enabled effective removal of the insulating ligands on FAPbI3 CQDs while preserving perovskite cores. Owing to the enhanced inter-dot electrical coupling, a power-conversion efficiency of 8.38% was demonstrated. Furthermore, the FAPbI3 CQDs-based devices showed superior stability over those of bulk FAPbI3 devices. Thermodynamic and crystallographic analyses revealed that enhanced contribution of the surface energy and lattice contraction contribute to their superior stability.