Photovoltaic device

1. A photoelectric conversion device comprising:

a crystalline semiconductor substrate having a first surface and a second surface; and

a first amorphous semiconductor layer formed over the first surface of the crystalline semiconductor substrate, wherein

an interface between the crystalline semiconductor substrate and the first amorphous semiconductor layer is an oxidized interface containing oxygen;

the first amorphous semiconductor layer comprises a high-oxygen-concentration region;

the oxidized interface has an oxygen concentration higher than an oxygen concentration of the high-oxygen-concentration region; and

the high-oxygen-concentration region has an oxygen concentration profile in which the oxygen concentration shown in a logarithmic scale is reduced stepwise in two or more steps from a side near the oxidized interface along a thickness direction of the first amorphous semiconductor layer;

the oxygen concentration profile comprises a first region, a second region, a third region, and a fourth region in this order from the side near the oxidized interface along the thickness direction of the first amorphous semiconductor layer;

the first region comprising a rising portion of a first step of the two or more steps;

the third region comprises a rising portion of the second step of the two or more steps;

the first region has a first slope, shown in a logarithmic scale, of the oxygen concentration from the side near the oxidized interface along the thickness direction, a magnitude of the first slope being defined as a first gradient;

the second region has a second slope, shown in a logarithmic scale, of the oxygen concentration from the side near the oxidized interface along the thickness direction, a magnitude of the second slope being defined as a second gradient;

the third region has a third slope, shown in a logarithmic scale, of the oxygen concentration from the side near the oxidized interface along the thickness direction, a magnitude of the third slope being defined as a third gradient;

the fourth region has a fourth slope, shown in a logarithmic scale, of the oxygen concentration from the side near the oxidized interface along the thickness direction, a magnitude of the fourth slope being defined as a fourth gradient; and

the second gradient and the fourth gradient are smaller than the first gradient and the third gradient.

2. The photoelectric conversion device according to claim 1 , wherein

the high-oxygen-concentration region is located in a region of 1 nm or less from the oxidized interface.

3. The photoelectric conversion device according to claim 1 , wherein

the semiconductor substrate is of n-type conductivity, and

the first amorphous semiconductor layer is an n-type amorphous semiconductor layer, the n-type amorphous semiconductor layer being located toward a light incident surface.

4. The photoelectric conversion device according to claim 1 , wherein

the semiconductor substrate is of n-type conductivity, and

the first amorphous semiconductor layer is a p-type amorphous semiconductor layer, the p-type amorphous semiconductor layer being located toward a light incident surface.

5. The photoelectric conversion device according to claim 1 , wherein the crystalline semiconductor substrate is of a first conductive type; and

The first amorphous semiconductor layer includes (i) an intrinsic amorphous semiconductor layer and (ii) an amorphous semiconductor layer of the first conductive type or of a conductive type opposite to the first conductive type, disposed in this order from the side near the oxidized interface.

6. The photoelectric conversion device according to claim 5 , wherein the high-oxygen-concentration region is provided within the intrinsic amorphous semiconductor layer.

7. The photoelectric conversion device according to claim 6 , wherein the oxygen concentration of the high-oxygen-concentration region is 1×10 20 /cm 3 or greater and 1×10 21 /cm 3 or less.

8. The photoelectric conversion device according to claim 5 , wherein the oxygen concentration of the high-oxygen-concentration region is 1×10 20 /cm 3 or greater and 1×10 21 /cm 3 or less.