Ligand Exchange on Oleylamine Passivated BaZrS3 Nanocrystals for Thin Film Creation

As the global transition towards renewable energy accelerates, perovskite materials are emerging as promising candidates for photovoltaic applications. Among these, the chalcogenide perovskite BaZrS₃ stands out due to its low toxicity and high stability when compared to common lead halide perovskites. Its direct band gap of 1.75-1.85 eV also makes it well-suited for some solar cell applications. BaZrS₃ nanocrystals have been colloidally synthesized at temperatures between 330°C and 365°C using molecular precursors. However, to be used in photovoltaic devices, these nanocrystal dispersions must be turned into high-quality films. Unfortunately, the surface of colloidally synthesized BaZrS₃ nanocrystals are typically passivated by oleylamine and oleic acid. These long bulky ligands hinder charge carrier mobility and reduce nanocrystal density on films, ultimately lowering efficiency. To address this, we propose procedures for exchanging these ligands for smaller inorganic ligands. In this work, we systematically screen various combinations of inorganic ligands, small organic ligands, and solvents to achieve well-dispersed, inorganic-capped BaZrS₃ nanocrystals. These nanocrystals are then spin-coated into thin films and characterized using scanning electron microscopy (SEM), UV-Vis spectroscopy, and energy-dispersive x-ray spectroscopy (EDX). Our goal is to produce films with improved quality, allowing for a more detailed investigation of their electronic properties and optimization for photovoltaic applications.