Interface properties of a-Si:H/c-Si heterojunction solar cells from admittance spectroscopy

The capabilities of admittance spectroscopy, in particular the dependences of the admittance upon frequency, temperature and applied bias, for the investigation of a-Si:H/c-Si heterojunctions are presented. Experimental results and results from a numerical modelling are described for n-type a-Si:H/p-type c-Si heterojunctions. These results compare very well and show that the admittance technique is sensitive to parameters of the a-Si:H/c-Si interface quality. The influence of different interface parameters, such as absolute value of defect density, hole and electron capture cross-sections is studied by the simulation. This simulation tool enables a detailed analysis of experimental results. In particular, it allows us to precise whether the capacitance signal is related to exchanges between interface states and electrons from the a-Si:H or (and) holes from the c-Si. The application of the admittance technique for a rapid a-Si:H/c-Si interface characterisation is discussed.