九州大学 エネルギー基盤技術国際教育研究センター

Energy Conversion Division -Tsuyoshi YOSHITAKE-

Photoelectric Conversion Technology

Associate Professor

Tsuyoshi YOSHITAKE

Specialization

photoelectric conversion

Affiliation

Faculty of Engineering Sciences

Research Topics

  • Fabrication of ultrananocrystalline diamond/hydrogenated amorphous carbon composite (UNCD/a-C:H) films by physical vapor depositions and their application to photovoltaics
  • Fabrication of semiconducting iron disilicides thin films by sputtering and their application to photovoltaics
  • Hetero-structural spintronics devices comprising ferromagnetic metals and semiconductors on the basis of Fe-Si system
  • Application of UNCD/a-C:H films as hard coating materials
  • Application of cubic AlxB1 xN thin films to the growth of single crystalline diamond films as buffer layers
  • Research Outline

    The laboratory devotes itself to education and research on new ecologically friendly materials applicable to photovoltaics and advanced electrical devices. Concretely, the target materials are semiconducting ultrananocrystalline diamond (UNCD)/hydrogenated amorphous carbon (a-C:H) composite (UNCD/a-C:H), which comprises a large number of diamond grains with diameters of less than 10 nm and an amorphous carbon matrix, and semiconducting iron disilicides. The research is mainly experimentally conducted and the experiment covers the growth in thin film by physical vapor depositions, the structural and optoelectrical evaluations of the films, and the fabrication of optoelectrical devices on the basis of the film preparation and processing such as lithography and etching. In other words, the research is consistently made from the elementary level of materials crystalline growth to the fabrication of devices such as photovoltaic cells.

Structural colors by chiral liquid crystal

Electron diffraction pattern of UNCD/a-C:H film and cross-sectional dark-field TEM image taken with a portion of diamond-111 ring.

Specific characteristics such as large optical absorption coefficients are generated owing to a huge number of grain boundaries between UNCD grains and those between UNCD grains and an a-C:H matrix involved in UNCD/a-C:H films.

Deep ultraviolet detection properties of heterojunction diodes comprising B-doped UNCD./a-C:H film and n-type Si substrate.

Deep ultraviolet detection properties of heterojunction diodes comprising B-doped UNCD./a-C:H film and n-type Si substrate.

Heterojunction diodes comprising p-type UNCD/a-C:H and n-type Si exhibit more than 70% external quantum efficiencies, which indicates that UNCD/a-C:H has a high potential as photovoltaic materials.

Target carbon solar cells comprising carbon photovoltaic layers and metal substrate

Target carbon solar cells comprising carbon photovoltaic layers and metal substrate

This is an ecologically friendly, durable, and low-cost solar cell that is compatible with present amorphous solar cells.