Amine-Free Synthesis of Colloidal Cesium Lead Halide Perovskite Nanocrystals

Colloidal cesium lead halide (CsPbX3) perovskite nanocrystals (PNCs) are of great interest in research because of their excellent optical properties and exceptional colour tunability. Oleic acid and oleylamine are the most commonly used surface capping ligands in colloidal CsPbX3 synthesis. The oleylamine plays an important role in surface passivation and maintaining colloidal stability. But in a long run, it is responsible for poor colloidal stability because of the facile proton exchange leading to the formation of labile oleylammonium halide, which pulls the halide ions out of the NC surface. By leveraging the synthetic toolboxes developed from decades of research into more traditional semiconductor nanocrystals, very recently researchers focused on developing various amine-free synthesis approaches to improve the colloidal and photostability of CsPbX3 perovskite NCs. In this review, we have summarized various amine-free based synthetic routes of CsPbX3 (X=Cl, Br, I) PNCs that are reported to date. We reviewed this progress in terms of their underlying synthetic approaches, and post-synthetic treatment steps. Furthermore, we reviewed and analyzed the prospects of these perovskite nanocrystals in terms of their photo-luminescence properties and device performances. In going forward, a deeper understanding of the role of precursors and ligands will significantly bolster the versatility of these amine-free PNC materials.