Direct fabrication of carbon nanotube-graphene hybrid films by a blown bubble method

Hybridization of carbon nanotubes (CNT) with graphene provides a promising means of integrating the attributes of both materials, thereby enabling widespread application. Here, we present a method to directly assemble hybrid CNT-graphene films by a blown bubble method combined with selective substrate annealing. We use polymethylmethacrylate (PMMA) as the polymeric matrix to blow bubbles containing self-assembled multi-walled CNT arrays, and then transform the bubble film into a CNT-graphene hybrid film by thermal annealing on a Cu substrate; PMMA serves as the carbon source for growing single to few-layer graphene among the CNT network until a continuously hybridized structure is formed. Compared to the bare (non-hybridized) CNT networks, the hybrid films exhibit improved electrical conductivity and structural integrity. Our method also enables the fabrication of a multi-walled CNT-Si solar cell, which has high power conversion efficiency, through the assembly of hybrid CNT-graphene structures.