(70f) Synthesis of Ternary Metal Phosphide Nanocrystals for Optoelectronics

Our growing energy usage has created an urgent need for sustainable sources of electricity and devices including photovoltaics and lighting. Successful development of such technology relies on the discovery of scalable photonic materials that can compete with current state-of-the-art III-V (GaN, GaAs) semiconductors, but have low toxicity and processing costs. Comprising of abundant, non-toxic, and recyclable elements, we present II-IV-V₂ systems (II-IV-V₂, II: Zn, IV: Ge, Sn, V: P) as candidates for such applications. Ternary pnictides offer the potential of tuning the band gap via cation disorder at fixed compositions and nearly constant lattice parameters; ternary chemistry also enables self-doping due to off-stoichiometry, which can be used to control carrier concentrations. Realizing the potential of II-IV-V₂ materials, however, has been difficult to accomplish. Syntheses have typically led to impure materials due to the difficulty of controlling the presence of defect phases and anti-site defects, leading to uncontrollable optoelectronic properties. In this work, we present colloidal partial cation exchange reactions from II-V₂ to II-IV-V₂ nanoparticles as a means of controlling crystal growth and mitigating the presence of defects. The relationship between structure and optoelectronic properties are explored via x-ray diffraction, x-ray absorption spectroscopy, transmission electron microscopy, and optical spectroscopy.