Tailoring Ordered Mesoporous Titania Films via Introducing Germanium Nanocrystals for Enhanced Electron Transfer Photoanodes for Photovoltaic Applications

Based on a diblock-copolymer templated sol–gel synthesis, germanium nanocrystals (GeNCs) are introduced to tailor mesoporous titania (TiO₂) films for obtaining more efficient anodes for photovoltaic applications. After thermal annealing in air, the hybrid films with different GeNC content are investigated and compared with films undergoing an argon atmosphere annealing. The surface and inner morphologies of the TiO₂/GeO_x nanocomposite films are probed via scanning electron microscopy and grazing-incidence small-angle X-ray scattering. The crystal phase, chemical composition, and optical properties of the nanocomposite films are examined with transmission electron microscopy, X-ray photoelectron spectroscopy, and ultraviolet–visible spectroscopy. Special focus is set on the air-annealed nanocomposite films since they hold greater promise for photovoltaics. Specifically, the charge–carrier dynamics of these air-annealed nanocomposite films are studied, and it is found that, compared with pristine TiO₂ photoanodes, the GeNC addition enhances the electron transfer, yielding an increase in the short-circuit photocurrent density of exemplary perovskite solar cells and thus, an enhanced device efficiency as well as a significantly reduced hysteresis.