Structural study on Pr0.55(Ca[1-y]Sr[y])0.45MnO3 thin films on perovskite (011) substrate

Structural study on the photo-switching system Pr{0.55}(Ca{1-y}Sr y){0.45}MnO3 thin films on perovskite (011) substrate has been made with synchrotron radiation diffraction experiment. The insulating phase of y=0.20 sample was found to be an antiferro-orbital ordered phase with large lattice distortion and the ferromagnetic metallic phase of y=0.40 film show no distinct lattice distortion from the paramagnetic phase, which are very similar with (Nd,Pr)0.5Sr0.5MnO3 films. A striking contrast of the orbital ordered phase of y=0.20 film to (Nd,Pr)0.5Sr0.5MnO3 films was its untwinned structure.Comment: 8 pages, 4 figures. To be published in European Journal of Physics Special Topic

Direct Observation of Sub-picosecond Hole Injection from Lead Halide Perovskite by Differential Transient Transmission Spectroscopy

Efficient charge separation at the interfaces between the perovskite and with the carrier transport layers is crucial for perovskite solar cells to achieve high power conversion efficiency. We systematically investigate the hole injection dynamics from MAPbI$_3$ perovskite to three typical hole transport materials (HTMs) PEDOT:PSS, PTAA and NiO$_x$ by means of pump-probe transmission measurements. We photoexcite only near the MAPbI$_3$/HTM interface or near the back surface, and measure the differential transient transmission between the two excitation configurations to extract the carrier dynamics directly related to the hole injection. The differential transmission signals directly monitor the hole injections to PTAA and PEDOT:PSS being complete within 1 and 2 ps, respectively, and that to NiO$_x$ exhibiting an additional slow process of 40 ps time scale. The obtained injection dynamics are discussed in comparison with the device performance of the solar cells containing the same MAPbI$_3$/HTM interfaces.Comment: 5 pages, 5 figure

Polar Antiferromagnets Produced with Orbital-Order

Polar magnetic states are realized in pseudocubic manganite thin films fabricated on high-index substrates, in which a Jahn-Teller (JT) distortion remains an active variable. Several types of orbital-orders were found to develop large optical second harmonic generation, signaling broken-inversion-symmetry distinct from their bulk forms and films on (100) substrates. The observed symmetry-lifting and first-principles calculation both indicate that the modified JT q2 mode drives Mn-site off-centering upon orbital order, leading to the possible cooperation of "Mn-site polarization" and magnetism.Comment: 5 pages, 4 figure

Metal nanoparticles in a photovoltaic cell: Effect of metallic loss

We examined numerically the contribution of contrasting characteristics of metal nanoparticles, strong polarization and metallic loss, to the total efficiency of photovoltaic cells. A layer of nanoparticle array was chosen as a model. We found that depending on the location of the layer in the cell, the metallic loss offsets the enhanced photoabsorption due to the strong near field. A general procedure to reduce a nanoparticle layer into a sheet of effective continuous medium is presented, which greatly facilitates the quantitative analysis