Effect of band offset on the open circuit voltage of heterojunction CuIn_1-xGa_xSe₂ solar cells

The reasons behind why the theoretically estimated open circuit voltage (V_oc) of CuIn_1-xGa_xSe₂ solar cells with large x values has not been realized are discussed. Typically, the reduction in V_oc is estimated only on the basis of the conduction-band offset between the absorber and the window material. The importance of the electron affinity difference between the window and the transparent electrode must also be taken into account. Based upon both of these factors, a material selection guideline is reported for the window and the transparent electrode layers suitable for high-x CuIn_1-xGa_xSe₂ absorber-based solar cells.