Laser-induced graphene as a sustainable counter electrode for DSSC enabling flexible self-powered integrated harvesting and storage device for indoor application

Dye-sensitized solar cells (DSSCs) are gaining a newfound interest thanks to their superior ability to harvest indoor light with efficiency higher than other photovoltaic technologies. This study reports, for the first time, the possibility of using laser-induced graphene (LIG) as a flexible counter electrode material for DSSCs. A flexible LIG (F-LIG) electrode was fabricated by direct laser writing of a polyimide film, without the need of a starting conductive substrate. The prepared electrodes showed a higher catalytic activity towards the reduction of I3 − / I − with respect to a more expensive Pt-based counter electrode. Moreover, the F-LIG electrodes outperformed electrodeposited PEDOT as a catalytic material for reduction of a copper bipyridyl complex (Cu(II/I)(tmby)2TFSI2/ 1) electrolyte. The F-LIG based DSSCs showed an open circuit voltage as high as 0.94 V and an increase in photoconversion efficiency higher than 60% with respect to the PEDOT-based counterpart, stepping from 3.08% to 4.96%. Thanks to the easy one-step laser-based fabrication process, the LIG-based DSSC was integrated with a LIG-based supercapacitor (SC), obtaining a flexible energy harvesting and storage system that was able to selfcharge both under simulated solar illumination and under indoor artificial illumination, appearing to be a promising energy source for the next generation of self-powered connected Internet of Things devices