Survey of dopant-free carrier-selective contacts for silicon solar cells

In recent years a significant amount of effort has been devoted towards the development of dopant-free carrier selective contacts for crystalline silicon (c-Si) solar cells. This short manuscript surveys a range of materials which have the potential to induce carrier-selectivity when applied to c-Si, including metals, metal oxides, alkali / alkaline earth metal salts, and organic conductors. Simple Ohmic test structures are used to assess the selectivity of these materials, that is, hole contacts are tested on p-type c-Si and electron contacts on n-type c-Si. Among these alternatives, a number of systems with exceptional potential are identified.