Soluble Hybrid Ionic Semiconductor and Its Photovoltaic Effect in Solution

Semiconductor materials were adopted in their solid states for photovoltaic applications owing to their nonsolubility and/or breaking of the photogenerated carrier transfer pathway in solution. The liquid-state photovoltaic device fills in a gap between currently prevailing full-solid-state and solid-liquid-state solar cells; however, reports on the photovoltaic effect from realistic semiconductor solution are absent so far. Herein, we report a hybrid inorganic-organic ionic semiconductor [Ni(Phen)₃][V₁₄O₃₄Cl]Cl (Phen = 1,10-phenanthroline) and observe its photovoltaic effect in ionic liquid solution. This photovoltaic effect arises as a result of charge transfer between the coordination cation and inorganic polyoxovanadate in solution under illumination and subsequent transfer to electrodes. The liquid-state photovoltaic device (cell configuration: carbon cloth||[Ni(Phen)₃][V₁₄O₃₄Cl]Cl in ionic liquid||Al foam) yields an open-circuit voltage of ca. 1.199 V and a photocurrent density of 3.268 mA cm^-2 upon illumination using an air mass of 1.5 (100 mW cm^-2) at 80 °C with a fill factor of 42.48% and an efficiency of 1.665%. This novel type of hybrid ionic semiconductor possesses great structural tunability for an optimized photovoltaic performance.