Efficient electron contacts for $n$-type silicon solar cells using Magnesium metal, oxide, and fluoride

The simplicity and low thermal budget of dopant-free, selective carrier contact materials is opening up new possibilities for low-cost, high performance silicon photovoltaics. This paper describes recent progress in the exploration of magnesium and related materials such as magnesium oxide and fluoride as electron-selective contacts to lightly doped n-type cSi. A direct comparison between the three materials permits to identify significant differences in transport and recombination behaviour. All three are incorporated in n-type silicon solar cells to demonstrate their actual performance at the device level. In particular, a simple aluminium electrode, functionalized with a nanoscale Mg-based layer, significantly enhances the performance of n-type c-Si solar cells, to a conversion efficiency of ~20% equivalent to the performance of the standard p-type silicon solar cells with an alloyed Al full-area hole contact.