Hokkaido University Research Profiles


High-efficiency Semiconductor Solar Cells

New-type solar cell consisting of a multi-striped semiconductor with orthogonal photon-photocarriers that was coupled to a waveguide.

Temperature rise and device degradation are suppressed by simultaneous optimization of light absorption and photocarrier collection, as well as photoelectric conversion over the entire solar spectrum by multiple semiconductor stripes. This leads to the realization of a highly efficient 2-dimensional PhotoReceptoConversion Scheme (2DPRCS).

Content of research

In conventional solar cells, there is a trade-off between carrier collection and the number of absorbed photons because the photo carrier migration direction and the light travel direction are parallel. Based on the orthogonality between the carrier migration direction and the light travel direction, it was possible to optimize both the light absorption and the carrier collection efficiency. Since the sunlight is sequentially photoelectrically converted from high- to low-energy components over the entire spectrum, thermal dissipation is minimized and high efficiency can be achieved. A waveguide type light collection system with a light wave direction conversion membrane can realize a photovoltaic system that is resistant to diffuse light. By preventing high-energy photons from entering the mid-gap and narrow-gap semiconductors, bond degeneration can be prevented and the life of the device can be extended. It is possible to realize the ultimate concentrator solar cell system, which is strong even in cloudy weather, has high conversion efficiency close to the thermodynamic limit, and is highly reliable.

  • Fig. 1: Scheme for improving the conversion efficiency by clarifying the dependence of conversion efficiency η on α and μ.

  • Fig. 2: Structure of the new photoelectric conversion element (the bottom-right interpolation figure is its cross-sectional view, Wk[k=1-4] is the stripe width of each cell). The bottom-left interpolation figure shows a conventional solar cell.

Potential for social implementation

  • ・The waveguide-coupled type can be applied to the windows and walls of buildings.
  • ・Waveguide-coupled surface structures can be attached to the surface of, or otherwise applied to bags, personal belongings that one carries around and automobiles.

Appealing points to industry and local governments

・We would like to take advantage of the characteristics of the all-in-one system to enter the market for applications that cannot be realized with conventional photovoltaic technologies, such as converting roof tiles and wall materials themselves into solar cells by using attachments, etc.
・We hope to conduct joint research with companies that have technologies for low-loss waveguides, multilayer thin-film waveguides and structured waveguides.

Intellectual property related to this research

特願2014-542164 「光電変換装置、建築物および電子機器」
特許第4022631号 「太陽電池および光電変換素子」
特許第5392795号 「太陽電池および光電変換素子」