A strong electric field and a high charge carrier density can be induced at interfaces between ionic conductors and electronic conductors such as semiconductors and metals. Consequently, remarkable properties, including electric field induced superconductivity and other electronic phase transitions, can be realized at the interfaces. The new interdisciplinary concept “iontronics”, electronics controlled by ions, is now rapidly developing as a method to explore the functions and properties of materials beyond the conventional electronics and ionics.

We present a method for accessing the balance sheets of energy and carriers as well as the respective sub-cell photovoltaic properties and internal luminescence yields in multi-junction solar cells by measuring the absolute electroluminescence quantum yields. This method was applied to a InGaP/GaAs/Ge 3-junction solar cell for satellite use. We calculated the conversion-efficiency limit and the optimized bandgap energy in 2-, 3-, and 4-junction tandem solar cells including finite values of sub-cell internal luminescence quantum yields to account for realistic material qualities in sub-cells. The results provide realistic targets for efficiency limits and improved design principles for practical tandem solar cells.

For every person and every season, the appearance and texture of human skin are different. That is caused by the structure of the skin tissue and the distribution of pigment cells. Tomographic images of human skin of various colors have been seen by using One Shot UV-Visible Spectroscopic Domain Optical Coherence Tomography. We show the tomographic images of human skin for each color and potential applications through a discussion about those images.

A new research field for “Group-IV semiconductor spintronics”, which utilizes the spin degree of freedom in silicon or germanium, has emerged in recent years. The scientific insight obtained in this field is expected to provide novel functionalities to existing device technologies. In this article, state-of-the-art studies concerning group-IV spintronics will be presented.

We have found that electron beam radiation or plasma treatment of the extracellular substances (ECS) of drosophila’s maggots allowed them to survive in the high vacuum environment of a scanning electron microscope (SEM). The plasma-polymerized nano-film of the ECS act as a protective layer against the rapid dehydration under the reduced pressure of SEM observation. An artificial coating of an amphiphilic substance such as the non-toxic compound polysorbitan monolaurate (Tween-20) allowed organisms without a natural ECS to survive under the SEM experiment. We have proposed the novel method of a “nano-suit” for high resolution SEM observation of living specimens.

The analysis of surface strain in polymer films with large bendability is essential for designing electronic devices, medical materials and wearable devices. Here we show a facile strain analysis of flexible films by a surface labeled grating method. Silicone elastomer films with a surface labeled grating were fabricated with a silicon substrate with a periodic structure. The surface strain of flexible films due to bending was analyzed by a change in the diffraction angle of a probe beam.

In order to perform precise measurement of electrical characteristics, it is important to only capture the true signal. To do this, it is necessary to reduce the noise as much as possible and amplify the signal. Here, I explain the equipment for measuring a very small signal, and the methods for reducing the noise, such as with filters, ground, wiring, and so on.