Electro-Optical Properties of Colloidal Semiconductor Nanocrystals Made by Means of Coalescence

The following work introduces a novel approach for shape and size control of semiconductor nanocrystals within colloidal solution by thermodynamically-driven aggregative growth. The presented technique is based on the employment of coordinating ligands that reduce surface energy, resulting in crystal melting. Compared to traditional growth approaches with precursors, here, nanoparticles act as building blocks offering more predictive control over the course of coalescence. We demonstrate that an innovative approach to thermodynamically-driven aggregative growth of colloidal semiconductor nanocrystals yields unique and diverse geometries (cubes, spheres, nanorods, nanorings) with narrow size dispersion by the use of X-, L-, and Z-type coordinating solvent, making it a valuable technique for the development of new optoelectronic materials. We also investigated the effect of external electric field on products of thermodynamically-driven aggregative growth. It was shown that solution-proceeded semiconductor nanocrystals undergo photoinduced rotation driven by excited-state dipole moment and counterbalanced by the viscosity of a solvent. Compared to solid assemblies, where dipoles are randomly positioned, solution-proceeded nanocrystals align along electric field and cause prominent optical changes due to quantum confined Stark effect. We demonstrate that organized alignment can be preserved by slow crystallization from a solid environment. This unique approach could aid the development of new electro-optical and voltage-sensitive devices for exotic applications