Development of Colloidal Halide Perovskite and Pnictide Nanocrystals for Optoelectronics

The semiconductor nanocrystals (NCs) have gained significant attention in the recent times due to their outstanding optoelectronic performance. Obtaining practical applications is still a great challenge. This requires better understanding of NCs w.r.t. to its optical properties. In this thesis, I focus on three emerging semiconductor NCs, i.e., CsPbBr3/m-SiO2 nanocomposites, Bi-doped Cs2Ag1-x-yNaxKyInCl6 NCs, and InAs NCs. I synthesize them such that to obtain new functionalities pertaining to their respective optical properties. Firstly, I employ a molten salt synthesis method to prepare CsPbBr3/m-SiO2 nanocomposites. The 100-nm-sized nanocomposites feature an optimal green photoluminescence (PL) emission of 517 nm along with a PL quantum yield (QY) as high as 77%. Additionally, it also exhibits the good stability against high flux, high temperature, high humidity and even aqua regia, making it ideal for practical applications. Thereby I employ it as a green color conversion layer in liquid crystal displays (LCDs). It provides a superior white emission performance compared to reference commercial LCD (Dell XPS 15 7590 laptop). Secondly, Bi-doped Cs2Ag1-xNaxInCl6 double perovskite (DP) NCs are synthesized through a new route of avoiding the formation of Ag0 on NCs surface, which makes DP having a high PLQY of ~60%. Then, the PLQY value further reaches to ~70% by a replacement of Na+ with K+ cations, forming alloyed Bi-doped Cs2Ag1-x-yNaxKyInCl6 NCs. Such an improvement of PLQY is attributed to an increase of surface ligand density in the presence of K+ cations. Thirdly, I did a colloidal chemistry synthesis of InAs NCs via the amino-As precursors. In this synthesis, surfactants are systematically varied to control the size, size distribution and morphology of InAs NCs. Notably, the InAs NCs, produced when using a specific combination of trioctylamine (TOA) and oleylamine (OA), have a good size distribution and show a tetrapod-like shape that is composed of a core size of ~2.5 nm, and arm lengths of 5-6 nm growing along 111 directions. InAs tetrapods are passivated mostly by OA with a minor fraction of TOA. Consequently, the combined use of TOA and OA (at high TOA:OA ratio of 4:1) leads to a low surface ligand density of InAs NCs, eventually resulting in the formation of InAs tetrapods.