Mechanistic Exploration of Dodecanethiol-Treated Colloidal CsPbBr3 Nanocrystals with Photoluminescence Quantum Yields Reaching Near 100%

Metal halide perovskite nanocrystals (NCs) are attractive materials for optoelectronics. However, further improvements in stability, reproducibility, and photoluminescence quantum yield (ΦPL) are essential for enabling future applications. Inadequate surface passivation is a major cause of instability, irreproducibility, and less than unity ΦPL. Herein, we probe the influence of multiple ligand binding groups on the colloidal stability and ΦPL of CsPbBr3 nanocrystals (NCs). We find that post-synthetic treatment with dodecanethiol reproducibly yields highly stable NCs with near-unity ΦPL for a range of synthetic conditions and initial ΦPL of the as-synthesized NCs. A mechanistic investigation shows that thiol addition leads to thioether formation via the thiol–ene reaction with octadecene, oleic acid, and oleylamine. Both thiolates and thioethers are suspected to bind to undercoordinated Pb atoms on the NC surfaces, and this surface binding can be rapidly accelerated through exposure to blue or UV light. Furthermore, we show that metallic Pb nanoparticles appear in many batches of synthesized CsPbBr3 NCs and that dodecanethiol addition eliminates these metallic Pb particles.