A hole transport layer (HTL) composed of spiro-OMeTAD as a hole transport material (HTM) in a perovskite solar cell (PSC) with CH3NH3PbI3 as a light-absorber was characterized by observing the performance of the cell with variation of the condition in HTL and correlating the result with the electronic structure of the layers, through which positive holes are transferred. While the time-dependent in- crease in the work function of the Au anode, the doping of a spiro-OMeTAD layer with Li-TFSI and tBP, and the light irradiation increased the short-circuit current and the open-circuit voltage, they made the Fermi level of the HTL deeper and closer to the HOMO level of the spiro-OMeTAD layer. Namely, the changes in the performances and the electronic structures are in accord with each other to indicate that the transport of positive holes in the spiro-OMeTAD layer was disturbed by positive hole traps in the layer, and could be improved by the changes in the condition of the layer, which decreased the depth and density of positive hole traps. It is noted that the Fermi level of the HTL with high performance should be much lower than that of the systems in equilibrium with ambient atmosphere, providing a problem to be solved for the stabilization of PSC.

View full abstract

Highly sensitive nuclear emulsion films and high-speed imaging technology have been developed for recording tracks of minimum ioniza- tion particles such as cosmic-ray muons and electrons. The ionization energy of the heavy ions in cosmic rays is too high to identify the indi- vidual nuclear charges because the signal of pulse-height volume for tracks is saturated on this system. We have developed desensitized nucle- ar emulsion films by adding a rhodium compound (Na3RhCl6∙5H2O). This modification reduces the film's sensitivity to heavy ions by 37%, resulting in better linearity between ionization energy and the signal of the tracks. The signals due to heavy ions were compared with the sig- nals recorded on a CR-39 nuclear track-detector. The desensitized nuclear emulsion films successfully distinguished adjacent nuclear charges of heavy ions.

View full abstract

We performed multi-resolution analysis using the wavelet transform on components of surface reflections from a facial image to identify wrinkles and fine asperities. Additionally, by applying principal component analysis, we statistically analyzed relationships between distribu- tions of the wrinkles and surface asperities, and actual ages. In previous research, the components of facial surface reflection were calculated as for multi-resolution analysis, however, the uneven illuminance on the face affected the trend. Therefore, we proposed a method to transform the luminance unevenness of facial images into a uniform distribution using signal processing, which contributes to the appropriate analysis of the surface reflection components on the face. As a result, compared with previous research, we could analyze the lighting unevenness with less influence of bias and acquire the distribution tendency of wrinkles and fine asperities in each direction.

View full abstract