Principles of carrier-selective contacts based on induced junctions

The applicability of different high (low) work function thin films for the formation of alternative hole (electron) selective contacts is currently (re-) explored for silicon solar cells. To provide some insight into contact schemes based on induced junctions their operation principles, important design parameters and losses are reviewed experimentally and with the help of numerical device simulations. Simulations with Sentaurus TCAD are used to address the importance of the work function and an efficient tunneling transport. It is highlighted that ""non-selective"" contacts will not obey the standard diode theory. This calls for an adapted loss analysis and one approach for this is presented for different hole contacts prepared by evaporation, sputtering, atomic layer deposition and PECVD. The results show that the ""classical"" electrical losses of selective contacts, like recombination and ohmic transport which are well quantified by J0 and the ohmic contact resistance, are not sufficient for the evaluation of ""non-selective"" contacts.