Optimisation of amorphous and polymorphous thin silicon layers for the formation of the front-side of heterojunction solar cells on p-type crystalline silicon substrates

In this study, we investigate the properties of n-doped amorphous silicon layer a-Si:H(n) combined with intrinsic thin silicon film deposited on high quality p-type CZ crystalline silicon, aiming at developing high performance heterojunction solar cells. The interface characteristics are analysed using Transmission Electron Microscopy TEM and capacitance measurements versus temperature and frequency. The insertion of a thin silicon film at the interface deposited under conditions of polymorphous material drives to a different structure of the interface. Our best front side heterojunction solar cells achieve 15% efficiency on 25 cm², with an open-circuit voltage of 634 mV. A maximum open-circuit voltage of 676 mV has also been obtained on polymorphous/crystalline heterojunctions with a high quality rear local BSF, indicating the excellent interface passivation achieved with the intrinsic layer deposited in conditions of polymorphous silicon. This experimental study reveals the clear potential of p-type substrates for the development of amorphous/crystalline heterojunctions solar cells.