A Directed Route to Colloidal Nanoparticle Synthesis of the Copper Selenophosphate Cu₃ PSe₄

The first colloidal nanoparticle synthesis of the copper selenophosphate Cu₃ PSe₄ , a promising new material for photovoltaics, is reported. Because the formation of binary copper selenide impurities seemed to form more readily, two approaches were developed to install phosphorus bonds directly: 1) the synthesis of molecular P₄ Se₃ and subsequent reaction with a copper precursor, (P-Se)+Cu, and 2) the synthesis of copper phosphide, Cu₃ P, nanoparticles and subsequent reaction with a selenium precursor, (Cu-P)+Se. The isolation and purification of Cu₃ P nanoparticles and subsequent selenization yielded phase-pure Cu₃ PSe₄ . Solvent effects and Se precursor reactivities were elucidated and were key to understanding the final reaction conditions.