Interface Limits to Solar Efficiency in Chalcopyrite (p)/Silicon (n) Hetero-junction Solar Cells

Jian WU1,2, Xusheng WANG1,2, Lingjun ZHANG1,2 1Canadian Solar Inc, Suzhou, China /2Photovoltaic Research Institute of Soochow University, Suzhou, China

Silicon based chalcopyrite (with the compounds composition I(B)-III(A)-VI(A)2) hetero-junction solar cells have been reported with the potential of high conversion efficiency theoretically. The hetero-junction 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-junction solar cells were studied by the means of numerical analysis with AMPS-1D simulation.  Our results indicates 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 (NDB) in ODC layer should be controlled lower than 1×1018cm-3, and the density of ODC/c-Si interface state (Dit) should be lower than 1×1013cm-2, to obtain the best cell performance.