Polymorphism in tetra-aryl biphenyl diamine hole transport materials: resolving the conflicting literature on N, N′-diphenyl-N, N′-bis(3,3′-methylphenyl)-[(1,1′-biphenyl)]-4,4′-diamine by high-resolution powder diffraction

The existence of a second polymorphic form of the hole transport material N,N′-diphenyl-N,N′-bis(3,3′-methylphenyl)-[(1,1′-biphenyl)]-4,4′-diamine has been confirmed using both Pawley and Rietveld refinement of structural information against high-resolution synchrotron X-ray powder diffraction data.