Promoting green innovation

To promote green innovation, AIST is developing technologies for increased use of alternative energy technologies, such as renewable energy sources that reduce greenhouse gas emissions (energy creation), high-density storage of energy (energy storage), highly efficient conversion and use of energy (energy saving), effective utilization of energy resources, and evaluation and reduction of environmental risks.

New Research Results

Development of Photo-Absorber Layer as a Promising Top Cell for Tandem-Type Solar Cells

A researcher at AIST has developed a technology to improve the photovoltaic efficiency of wide-bandgap CIS-type thin-film solar cells that do not contain the rare metal indium.
For tandem-type solar cells, which are expected to achieve even higher performance than the solar cells currently in widespread use, the development of top cell materials for short-wavelength light absorption that satisfy all the elements of "low cost," "high performance," and "high reliability (stability)" has been a challenge. In this study, we developed a technology to improve the quality of photo-absorber layers with a wide bandgap energy, which is particularly suitable as a top cell among CIS-type compounds, a promising material group that satisfies these elements. The newly developed photo-absorber layer has excellent stability and is expected to be applied to inexpensive, high-performance, and flexible tandem-type solar cells in the future.

Successful enhancement of energy conversion efficiency in CIS-type solar cells specialized for absorbing short-wavelength illumination
^* Figures from the original paper have been cited and modified.

Development of New Thermoelectric Materials that Generate Electricity Perpendicular to Heat Flow

Researchers at AIST, in collaboration with Shimane University, have succeeded in developing a unique thermoelectric material (goniopolar material) that can orthogonalize temperature differences and current direction.
Most primary energy is discharged as heat, and to make effective use of this unused heat (waste heat), development of thermoelectric materials that convert heat into electricity is underway worldwide. In recent years, new materials with high performance have been reported one after another, but only Bi₂Te₃ based materials, which were discovered more than half a century ago and operate near room temperature, have been put to practical use. The lack of practical thermoelectric modules that can operate at temperatures higher than room temperature has hindered progress in power generation using waste heat. In particular, conventional thermoelectric modules have a "longitudinal" configuration in which the heat flow and the power generation direction are the same, which causes elemental diffusion and other reactions at the electrode interface in contact with the high-temperature heat source during power generation, leading to degradation, which poses a durability challenge. The research group fabricated single crystals of Mg₃Sb₂ and Mg₃Bi₂ with precisely controlled carrier density and discovered an extremely unique property (goniopolarity) that leads to the realization of "transverse" thermoelectric modules in which the heat flow and power generation direction are orthogonal. The transverse thermoelectric module does not require electrodes at the high-temperature side of the module, which prevents thermal degradation, and is expected to drastically solve the durability issue that has been the bottleneck of conventional thermoelectric modules.
First-principles calculations were performed to elucidate the origin of the goniopolarity, and it was found that the sign of charge carriers differs depending on the crystallographic direction due to the anisotropy of the electronic structure. Since there are many materials with similar characteristics, the application of the method used in this study is expected to lead to the development of thermoelectric modules with higher performance.

Schematic diagram of conventional (temperature difference and current are parallel) and new type (temperature difference and current are orthogonal) thermoelectric modules

Open Innovation Laboratory

Since FY 2016, as a part of the “Open Innovation Arena concept” promoted by the Ministry of Economy, Trade and Industry (METI), AIST has created the concept of “open innovation laboratories” (OILs), collaborative research bases located on university campuses, and has been engaged in their provision. We are planning to establish more than ten OILs by FY 2020.

AIST will merge the basic research carried out at universities, etc. with AISTʼs goal-oriented basic research and applied technology development, and will promote bridging research and evelopment and industry by the establishment of OILs.

Cooperative Research Laboratories

In order to conduct research and development more closely related to strategies of companies, we have established collaborative research laboratories, bearing partner company names.

Partner companies provide their researchers and funding, and AIST provides research resources, such as its researchers, research facilities, and intellectual property. The loaned researchers of companies and AIST researchers jointly conduct research and development.

By setting up cooperative research laboratories, we will accelerate the commercialization of our goal-oriented basic research and application research with partner companies.