Surfactant-free synthesis of sub-stoichiometry tungsten oxide nanoparticles and their use as anode buffer layers in organic solar cells

摘要

Abstract A surfactant-free synthesis of small-sized tungsten trioxide is presented. Nanoparticles with an average size of 4.6?±?1.5?nm are prepared via hot-injection techniques in ethanol. Due to the reducing properties of ethanol, a sub-stoichiometry composition WO3-x (x～0.4) is obtained. The partial reduction of W+VI to W+V becomes visible in the bluish color of suspensions and powder samples and in optical spectroscopy (UV-Vis). The nanoparticles are further characterized by transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDXS) and infrared spectroscopy (FT-IR). Due to their small size, their high colloidal stability and the absence of surfactants, layers from the as-prepared WO3-x nanoparticles are ideally suited to form anode buffer layers in organic solar cells. Exemplary solar cells show good power conversion efficiency of 6.3%. Graphical abstract Display Omitted Highlights ? Surfactant-free synthesis of small-sized tungsten trioxide (4.6?±?1.5?nm) made via hot-injection techniques in ethanol. ? Sub-stoichiometry composition WO3-x (x～0.4) proven by bluish color of suspensions and powder samples, optical spectroscopy, and electron microscopy. ? Colloidally stable suspensions in ethanol without the need of additional stabilizers. ? Conceptual use in organic solar cells showing good power conversion efficiency of 6.3%. ]]>