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

Abstract

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/GeOx 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.

Operando Study of Structure Degradation in Solid‐State Dye‐Sensitized Solar Cells with a TiO2 Photoanode Having Ordered Mesopore Arrays

“…These characteristic peaks originate from the highly ordered mesoporous TiO 2 nanostructures. [37,38] To examine the structure changes, we perform horizontal line cuts at the Yoneda peak region of the mesoporous TiO 2 (i.e., Figure 2c; red box) due to its strong scattering signal prevailing over other materials. [37] The horizontal line cuts are shown for the small-pore and bigpore ssDSSCs in Figure 2d,e, respectively.…”

“…Via data modeling, two characteristic nanostructures are extracted, and the most pronounced features (peaks in Figure 2d,e; indicated with purple and green arrows) are caused by the small‐sized TiO 2 nanostructure having a highly ordered spatial distribution. This small‐sized structure represents the majority of the inner morphologies [ 38 ] and is thereby taken as an indication for morphology evolution during operation. Figure 2f,g shows the modeling results of the radius and the corresponding center‐to‐center distance of the small‐sized nanostructures for the small‐pore and big‐pore ssDSSCs, respectively.…”

“…In addition, the distribution width of the corresponding center‐to‐center distance in Figure 2j is found to increase, indicating that the spatial order of the nanostructure becomes worse. [ 38,39 ] The less‐ordered structure also causes a decrease in the peak intensity (Figure 2i). The larger domain radius with a decreased spatial‐order degree is mainly affected by two factors: 1) the structural variation of the mesoporous TiO 2 itself; and 2) the dye aggregation on the TiO 2 surface, which contributes to the bigger and coarser TiO 2 –dye interfacial structure.…”

Low‐Temperature and Water‐Based Biotemplating of Nanostructured Foam‐Like Titania Films Using ß‐Lactoglobulin

“…An estimation for the lower limit of the corresponding crystal sizes is calculated from the FWHM according to the Scherrer equation. [ 60 ] The results from the Gaussian fits are presented in Figure 4b–e and show the film formation on the crystalline length scale between the turning points A and B (Figure S3, Supporting Information) of the scanning area during the entire spray experiment. In more detail, the data shows the inner, central, and outer regions of the spray cone.…”

“…To extract the lateral information, the horizontal line cuts were modeled by applying cylindrical form factors on a 1D paracrystal in the framework of the distorted wave Born approximation (DWBA), using the effective interface approximation (EIA) in combination with the local monodisperse approximation (LMA). [ 60 ] This lateral information was modeled in terms of form factors (structure sizes) and structure factors (center‐to‐center distances). 2D GIWAXS images were reshaped with the MATLAB‐based software package GIXSGUI and 1D intensity distributions as functions of q (Å −1 ) were obtained by azimuthal integration.…”