Highly crumpled graphene nano-networks as electrocatalytic counter electrode in photovoltaics

Highly crumpled graphene-based three dimensional (3D) interconnected and hierarchically porous conducting networks were prepared for application as electrocatalytic counter electrode (CE) in dye-sensitized solar cells (DSSCs). Finely and hierarchically crumpled graphene was synthesized from Fe₂O₃/graphene oxide (GO) hybrids via a one-step chemical etching-reduction process with HI solution. The synthesized crumpled graphene exhibited not only 24 times higher specific surface area, but also superior dispersibility in aqueous solution compared to conventional reduced graphene oxide (rGO). Owing to its superior solution processability and comparable electrical conductivity, the crumpled graphene could be assembled into 3D interconnected films on the substrates simply by drop casting, without any binders. In addition, although the crumpled graphene was not modified by dopants or high-temperature annealing, it showed much higher electrocatalytic activity for the I^-/I₃^- redox couple compared to that of rGO, which is mainly attributed to its significantly larger accessible surface area for electrochemical reduction. As a result, the DSSC containing the crumpled graphene CE exhibited 2.8 times enhanced conversion efficiency (η = 5.15%) compared to that containing a rGO electrode (η = 1.86%).