Deciphering the three-dimensional morphology of free-standing block copolymer thin films by transmission electron microscopy

► Block copolymer thin-film morphologies are deciphered using a multi-method TEM approach. ► Free-standing PS-b-PEO electrolyte films are cast onto holey substrates from various solvents. ► Various energy-filtered TEM techniques and electron tomography are applied. ► An unexpected layered honeycomb-type morphology is revealed.