'Graphene sandwich' unlocks solar cell properties of 2D crystal

Part of a raft of new research into possible uses for the atom-thick sheets of carbon atoms first discovered at Manchester, the new discovery shows how graphene can help harness the properties of light-senstive two-dimensional crystals, which could give rise to devices such as light-sensitive walls that could power whole buildings.

Since Andre Geim and Kostya Novosolev’s discovery that graphene can be made by peeling off single layers of graphite mechanically, several other similar single-layer materials have been found, the team says in a paper published in the journal Science. Moreover, stacking these crystals together with graphene has proved to be a useful way of unlocking the properties of these materials; for example, it’s allowed the team to create materials that could be used in flexible electronics.

The latest research uses a class of materials called transition metal dichalcogenides (TMDCs). These are actually three-layer materials, consisting of a single-atom thick lattice of transition metal atoms between two single-atom layers of sulphur, selenium or tellurium. The bonds within each layer are very strong, but those between the layers are quite weak — a similar structure to graphite. Examples of these materials are tungsten disulphide (WS₂), molybdenum disulphide (MoS₂) and niobium diselenide (NbSe₂).