Evolution of the solar cell performances with the germanium composition x of the ZnGeO buffer layer for different absorber doping concentration N_A using an absorber layer thickness of 2 μm and hole and electron mobilities of 25 cm²V⁻¹s⁻¹ and 50 cm²V⁻¹s⁻¹ respectively. Simulation are done using interface and defective layers at the heterojunction (dashed lines) as described in Section 1 and with an ideal heterojunction without such interface and defect layers (plain lines).