Investigations into low-temperature synthesis of colloidal BaZrS3 nanoparticles

Chalcogenide perovskites have exhibited the similar superior inherent properties for (photovoltaic) PV applications as halide perovskites. Moreover, they exhibit dramatic intrinsic stability and are comprised of benign and widely existing elements. Current research on chalcogenide perovskites predominantly focuses on synthesizing standard-phase BaZrS₃ (SP-BaZrS₃) with Pnma orthorhombic distorted perovskite structure. Through our group efforts, the original solid-state synthesis temperature for BaZrS₃, which was exceedingly high >1000 ℃, has been successfully reduced to below 600 ℃. Unfortunately, this reduced temperature solid-state synthesis approach does not produce significant photoluminescence (PL), indicating a high density of defects that suppress radiative recombination. Moreover, its elevated synthesis temperature renders it incompatible with current photovoltaic industry techniques. Therefore, my work focuses on exploring methods to restore PL. Building on my published work with my group members on solid-state synthesis, this research focuses on the synthesis of BaZrS₃ nanoparticles. This nanomaterial offers a promising approach for further reducing the synthesis temperature, making it compatible with PV device fabrication and enabling the production of uniform thin films without scattered islands. After gradually optimizing various reaction conditions and variables, I found out the current optimal route utilizing bis(pentametylcyclopentadienyl) barium and tetrakismethylethylamido zirconium precursors mixed with carbon disulfide in rigorously dried oleylamine solvent. Then, heat injection synthesis method was applied to decant the mixture into heating medium under environments devoid of oxygen and moisture. After extensive effort, we developed reproducible methods to ensure the synthesis of pure SP-BaZrS₃ nanoparticles. Furthermore, I identified strategies to prevent the formation of the irregular BaZrS₃ phase (IP-BaZrS₃)—a semi-crystalline, metastable phase that had long impeded the production of pure SP-BaZrS₃.