Calculated potential (with respect to the equilibrium Fermi-level, color-coded) and electron current flow (arrows) in a CIGSe/CdS/ZnO structure with an inverted grain boundary in the absorber (only one half of the grain is shown). Parameters for this calculation are shallow acceptor density in the absorber N_A = 10¹⁶ cm^-3, and carrier lifetimes τ of 1 ns. The cell is illuminated with monochromatic light (wavelength 1000 nm, power 100 mW/cm²).