Deep eutectic solvent route synthesis of zinc and copper vanadate n-type semiconductors – mapping oxygen vacancies and their effect on photovoltage

摘要: Ternary metal oxides M2V2O7−δ (M = Zn and Cu) were synthesized by dissolving binary oxide precursors in an environmentally benign deep eutectic solvent (DES), which is a mixture of hydrogen bond donor acceptor, followed annealing open crucible. The unique reaction environment provided the evolved ammonia allows for stabilization oxygen vacancies reduced oxidation states ions within matrix without need any post-treatment with flammable reducing agents. According to comprehensive characterization, including X-ray photoelectron spectroscopy (XPS), neutron powder diffraction, UV-vis spectroscopy, deficiency accompanied centers (Cu+ or V4+), resulting mixed-valence states. amount can be tuned changing temperature providing control over band gaps ternary mid-gap from centers. All vanadates are n-type semiconductors based on negative photovoltages obtained surface photovoltage (SPS). A decay increasing temperatures attributed electron trapping electron/hole recombination at V4+ Cu+ This work shows first time impact electronic structure DES solar energy conversion applications.