Expanded graphite/pencil-lead as counter electrode for dye-sensitized solar cells

A kind of new carbon material – expanded graphite (EG) was prepared and then used with 5B pencil-lead as counter electrodes for the DSSCs. The EG/pencil-lead products were discussed following five different weight ratios of 1:0, 1:1, 1:2, 2:1, and 0:1. And flake graphite was employed for comparison. Commercial P25 TiO 2 adsorbing dye N719 was used as photoanode and ionic liquid was adopted as electrolyte to compose the cell. Using green light-emitting diode (525   nm, LED) as the light source, J – V curves were recorded using the Zahner Zennium CIMPS system based on an IM6x electrochemical workstation. When the mass ratio of the mixture was 1:1, the overall conversion efficiency of DSSCs reached to highest value 7.7% ( J sc   =   0.441   mA   cm −2 , V oc   =   683   mV, fill factor   =   0.637) under green-light intensity.