By dipping the mesoporous TiO 2 film in Sr 2+ solutions and subsequent annealing, a modification layer of SrTiO 3 has been formed on the surface of the mesoporous TiO 2 film, and the effect of modification on the photovoltaic characteristics of the perovskite solar cells has been studied detailedly. The XPS and TEM results verified the existence and nature of the SrTiO 3 modification layer. Benifiting from the TiO 2 surface modification, the morphology of perovskite film and light absorption of the CH 3 NH 3 PbI 3 absorber have been improved effectively, and a faster charge transfer has also been achieved between the CH 3 NH 3 PbI 3 perovskite layer and the modified TiO 2 . As a result, an average conversion efficiency of 11.4% has been achieved in the perovskite solar cell based on the modified mesoporous TiO 2 by 10 mM Sr 2+ solution, and it increases approximately by 46% in comparison with the photovoltaic efficiency of 7.8% of the perovskite solar cell based the bare mesoporous TiO 2 layer.
A metal-clad optical waveguide sensor based on guided-mode resonance spectroscopy has been developed using a mesoporous TiO2 film as the chemical-sensitive core layer. The sol–gel block copolymer templated mesoporous TiO2 films are ∼275 nm thick, supporting both the transverse electric (TE) and transverse magnetic (TM) modes and thus providing the sensor with the TE- and TM-related dual sensitivities. Both the TE- and TM-mode resonance wavelengths (λR) at the same incident angle were obtained by broadband attenuated total reflection spectroscopy. The film porosity was determined to be ∼0.535 by using the combination of Fresnel formula and Bruggeman approximation to fit the measured values of λR. The TE- and TM-related sensitivities of the sensor to the two analytes of elaidic acid (EA) and Cr6+ were measured at the same incident angle. For each analyte, the TM-related sensitivity is higher than that with the TE-related one. The two sensitivities can be calibrated with each other. Moreover, by adjusting the block copolymer concentration in the coating solution, the mesoporous TiO2 films with different porosities were prepared for investigating the porosity dependence of the sensor’s sensitivity. The findings indicate that a larger-porosity TiO2 film can lead to higher sensitivity. The work demonstrated that the metal-clad mesoporous TiO2 film-based guided-mode resonance sensor is advantageous over a conventional SPR sensor for in situ detection of small molecules.
Bo Zhang,Hui Wang,Yiwei Lu,Yang Song,Yanlin Li,Yuanyuan Tian
Fabrication of electrochromic films with micro/nanostructures is one of the most feasible ways to improve their properties for high-performance electrochromic devices (ECDs). In this work, mesoporous TiO 2 and NiO electrochromic films are prepared by sol-gel technique with an auxiliary solvent of F108 (PEO 1 3 2 PPO 5 0 PEO 1 3 2 ). By adjusting the content of F108 and heat treatment temperature, the transparent and uniform mesoporous films are successfully prepared. The TiO 2 and NiO films are composed of inter-connected nanoparticles with a size of about 20 nm. The thicknesses of the films are about 300 nm and the mesoporous sizes are about 13 nm. The films have a short response time during the electrochromic process. When supplied with positive/negative voltages for 50 s, the coloring/bleaching times of TiO 2 and NiO mesoporous films are 15/13 and 17/12 s, respectively. The ECD fabricated with TiO 2 and NiO mesoporous films shows good electrochromic properties: short response time (14/19 s, for bleaching/coloring time), wide transmittance modulation range ( ∼ 37.21% at 540 nm), high coloration efficiency (CE) (100.6 cm 2 /C at 540 nm) and outstanding cycle stability (800 cycles). These are attributed to the mesoporous channels of films, which can increase reaction activity site, shorten ions transport path, and thus improve electrochromic reaction.
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