PTAA – poly[bis(4-phenyl)(2, 4, 6-trimethylphenyl)amine] – is a successful hole-transporting material for perovskite solar cells, but can only be applied using spin-coating, which is not suitable for wide areas, according to the research team. Blade-coating is compatible with large surfaces, but the physical properties of PTAA prevent it from forming even layers when blade coated, leaving voids within the finished solar cell.
Knowing this, the team went on a hunt for a hole transport that is compatible with blade coating.