Figure 4: (a) Simulated energy band diagram of the GaInP/Ga(In)As/CuInSe2 3J under illumination conditions and (b) a closeup of the energy band diagram at the compositionally graded buffer region composed of GaInP including the overshoot layer and the CuInSe2 based bottom subcell including a highly doped CuInSe2 back surface field (BSF).