Interfacial barrier is a key factor that determines the performances of heterojunctions.In this work,we study the effect of manganite film thickness on the effective interfacial barrier for La 0.67 Sr 0.33 MnO 3 /Nb:SrTiO 3 junctions.The barrier is extracted from the forward current-voltage characteristics.Our results demonstrate that the barrier decreases gradually from ～0.85 eV to ～0.60 eV when the film thickness decreases from 150 nm to 2 nm.The overall value of the barrier is only about 50% of the corresponding one determined from the photovoltaic effect.
Platinum nanoparticles(PtNPs)/graphene composite materials are synthesized by a controlled chemical reduction of H2PtCl6 on graphene sheets.The electrocatalytic activity of a PtNPs/graphene composite counter electrode for a dye-sensitized solar cell(DSSC) is investigated.The results demonstrate that the PtNPs/graphene composite has high electrocatalytic activity for the dye-sensitized solar cell.The cell employing PtNPs(1.6 wt%)/graphene counter electrode reaches an conversion efficiency(η)of 3.89% upon the excitation of 100 mW/cm2 AM 1.5 white light,which is comparable to that of the cell with a Pt-film counter electrode(η=3.76%).It suggests that one can use only 14% Pt content of the conventional Pt-film counter electrode to obtain a comparable conversion efficiency.It may be possible to obtain a high performance DSSC using the PtNPs/graphene composite with a very low Pt content as a counter electrode due to its simplicity,low cost,and large scalability.
The low temperature sample stage in a transmission electron microscope is used to investigate the charge ordering behaviours in a Bi 0.4 Ca 0.6 MnO 3 film with a thickness of 110 nm at 103 K.Six different types of superlattice structures are observed using the selected-area electron diffraction(SAED) technique,while three of them match well with the modulation stripes in high-resolution transmission electron microscopy(HRTEM) images.It is found that the modulation periodicity and direction are completely different in the region close to the Bi 0.4 Ca 0.6 MnO 3 /SrTiO 3 interface from those in the region a little further from the Bi 0.4 Ca 0.6 MnO 3 /SrTiO 3 interface,and the possible reasons for this are discussed.Based on the experimental results,structural models are proposed for these localized modulated structures.
