Spindle-like porous N-doped TiO2 encapsulated (Ca,Y)F2:Yb3+,Tm3+ as the efficient photocatalyst near-infrared range

Low-temperature processed tantalum/niobium co-doped TiO2electron transport layer for high-performance planar perovskite solar cells

A low-temperature preparation process is significantly important for scalable and flexible devices. However, the serious interface defects between the normally used titanium dioxide (TiO₂) electron transport layer (ETL) obtained via a low-temperature method and perovskite suppress the further improvement of perovskite solar cells (PSCs). Here, we develop a facile low-temperature chemical bath method to prepare a TiO₂ETL with tantalum (Ta) and niobium (Nb) co-doping. Systematic investigations indicate that Ta/Nb co-doping could increase the conduction band level of TiO₂and could decrease the trap-state density, boosting electron injection efficiency and reducing the charge recombination between the perovskite/ETL interface. A superior power conversion efficiency of 19.44% can be achieved by a planar PSC with a Ta/Nb co-doped TiO₂ETL, which is much higher than that of pristine TiO₂(17.60%). Our achievements in this work provide new insights on low-temperature fabrication of low-cost and highly efficient PSCs.

Hierarchical PANI/ZnO nanocomposite: synthesis and synergistic effect of shape-selective ZnO nanoflowers and polyaniline sensitization for efficient photocatalytic dye degradation and photoelectrochemical water splitting

Hierarchical nanoflowers (NFs) of zinc oxide (ZnO) have been synthesized in the hexagonal wurtzite structure by a facile hydrothermal method. Polyaniline (PANI) has been prepared by the chemical oxidative polymerization method and incorporated with ZnO NFs by the chemisorption method. The potential of the synthesized nanostructures has been demonstrated for efficient photocatalytic degradation of methylene blue (MB) and photoelectrochemical water splitting. The PANI/ZnO nanocomposite has exhibited the enhanced photocatalytic activity which is ∼9 fold higher in comparison to pristine ZnO NFs and enhanced photocurrent density which is ∼16 fold higher than the ZnO photoanode. Importantly, ∼4 fold increment in the incident photon-to-current conversion efficiency (IPCE) is exhibited by PANI/ZnO, than that of ZnO photoanode. The remarkably enhanced photocatalytic and photoelectrochemical performance of PANI/ZnO nanocomposite is attributed to the availability of more interfacial sites facilitated by the hierarchical ZnO NFs, improved overall photoresponse due to its photosensitization with PANI and the resulting type-II heterojunction between them, which helps in the efficient separation of photogenerated charge carriers at the interface. A plausible reaction mechanism for the substantially improved performance of nanostructured PANI/ZnO towards MB degradation and water splitting has also been elucidated.

The morphology evolution, tunable down-conversion luminescence, and energy transfer of [CaY]F2 crystals doped with Li+/Ce3+/Tb3

Octahedral [CaY]F2 crystals with an average particle size of 1 μm were synthesized via a mild one-step hydrothermal route without employing any surfactants. Various morphologies, including cubes, truncated cubes, truncated octahedrons, and spheres, were achieved via manipulating the amount of EDTA used, and a possible growth mechanism was proposed based on the surface energies of different crystal planes and the influence of the surfactant. XRD, SEM, EDS, TEM, HRTEM, and PL analysis were used to characterize the products. The effects of the morphologies and Li+ doping concentrations on the luminescence intensities of the [CaY]F2:Ce3+/Tb3+ phosphors were explored, and the strongest luminescence intensity is obtained when the sample is cubic with (100) crystal faces and the doping concentration of Li+ is 0.25 mol%. Additionally, multicolor emission (blue → aquamarine blue → green) was obtained from [CaY]F2:Ce3+/Tb3+ phosphors via adjusting the doping concentration of Tb3+, which resulted from the Ce3+ → Tb3+ energy transfer behavior; the energy transfer here happened through a dipole-dipole mechanism. This work may result in the as-synthesized phosphors having great application potential in many optoelectronic device fields, such as in displays and multicolor lighting.