| abstract |
Provided is a semiconductor element that, in the fabrication of fuel by means of carbon dioxide reduction utilizing sunlight and the fabrication of hydrogen fuel by means of water decomposition utilizing sunlight, makes it possible to utilize light in a wider range of wavelengths, and, by means of a low-cost element, to improve the efficiency of the carbon dioxide reduction reaction and the efficiency of the water decomposition hydrogen generation reaction. The semiconductor element has the following: an electrode layer (101); a first semiconductor layer (103); and a second semiconductor layer (102) having opposing first and second surfaces, the electrode layer (101) being disposed so that it is in contact with the first surface and the first semiconductor layer (103) being disposed so that it is in contact with the second surface. The semiconductor element is characterized in that the lower limit of the electrical potential of the conducting band of the first semiconductor layer is higher than the hydrogen generation potential (the methane or methanol reaction potential), the upper limit of the electrical potential of the valence band of the second semiconductor layer is lower than the oxygen generation potential, and the band gap of the first semiconductor layer is greater than the band gap of the second semiconductor layer. |