Interface limits to solar efficiency in chalcopyrite (p)/silicon (n) hetero-junction solar cells

Silicon based chalcopyrite (with the compounds composition I(B)-III(A)-VI(A)₂) hetero-j unction solar cells have been reported with the potential of high conversion efficiency theoretically. The hetero-j unction solar cell with PNN⁺ structure is fabricated as: front metal electrodes/ transparent conduction oxide (TCO)/ p-type chalcopyrite layer emitter/ n-type silicon base/ n⁺ silicon back surface doping/ rear metal electrodes. By inserting artificially one thin order defect compound (ODC) layers with a high bulk density of states, and one thin interface layer to represent the total interface states between the chalcopyrite and silicon, the impacts of the interface defects on PNN⁺ hetero-j unction solar cells were studied by the means of numerical analysis with AMPS-1D simulation. Our results indicate that band bending, determined by band offset at the ODC/c-Si hetero-interface, could be critical to cell performance. The optimum electron affinity of ODC layer is 4.4eV The total volumetric density of states (N_DB) in ODC layer should be controlled lower than 1×10¹⁸ cm³, and the density of ODC/c-Si interface state (D_it) should be lower than 1×10³ cm^-2, to obtain the best cell performance.