Solar cell and solar cell module

A solar cell, comprising:

• a semiconductor substrate of a first conductivity type which includes a first principal surface and a second principal surface on a back side of the first principal surface;
• a first semiconductor layer of the first conductivity type disposed above the first principal surface;
• and
• a second semiconductor layer of a second conductivity type disposed below the second principal surface, the second conductivity type being different from the first conductivity type, wherein
• the semiconductor substrate includes:
• a first impurity region of the first conductivity type;
• a second impurity region of the first conductivity type, which is an entire region between the first impurity region and the first principal surface and is a region including the first principal surface;
• and
• a third impurity region of the first conductivity type, which is an entire region between the first impurity region and the second principal surface and is a region including the second principal surface,
• the first impurity region and the second region are in contact with each other, and the first impurity region and the third impurity region are in contact with each other,
• a peak concentration of an impurity of the first conductivity type in the second impurity region is higher than a peak concentration of an impurity of the first conductivity type in the third impurity region,
• the peak concentration of the impurity of the first conductivity type in the third impurity region is higher than a peak concentration of an impurity of the first conductivity type in the first impurity region,
• a dose in a predetermined diffusion width of the second impurity region is greater than a dose in a predetermined diffusion width of the third impurity region,
• the semiconductor substrate is a monocrystalline silicon substrate,
• the first semiconductor layer and the second semiconductor layer are amorphous silicon layers,
• a concentration of an impurity of the first conductivity type in the first impurity region is 5×1013 cm−3 to 1×1017 cm−3,
• the peak concentration of the impurity of the first conductivity type in the second impurity region is 2×1018 cm−3 to 4×1019 cm−3, and
• the peak concentration of the impurity of the first conductivity type in the third impurity region is 1×1018 cm−3 to 2×1019 cm−3.