Thermoelectric conversion device and thermoelectric conversion module

A thermoelectric conversion device comprising:

• a first electrode;
• a thermoelectric conversion material portion containing Si and Ge as constituent elements and configured to convert heat into electricity;
• a conductive joining member disposed in contact with the first electrode and the thermoelectric conversion material portion and joining the first electrode and the thermoelectric conversion material portion together;
• and
• a second electrode disposed away from the first electrode and electrically connected to the thermoelectric conversion material portion,
• wherein the Si and the Ge contain an amorphous phase and a crystalline phase,
• the joining member contains at least one of Ag, Cu, Ti, and Sn or an alloy thereof as a major constituent,
• the thermoelectric conversion material portion includes
• a first layer containing the major constituent in an amount of 10 atm % or more and in contact with the joining member, and
• a second layer in contact with the first layer, and
• the second layer has a degree of crystallinity of 40% by volume to 90% by volume.