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 TiO2 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% (Jsc = 0.441 mA cm−2, Voc = 683 mV, fill factor = 0.637) under green-light intensity.

► Expanded graphite/pencil-lead was used as the counter electrode for dye-sensitized solar cells.
► The overall conversion efficiency of DSSCs reached to highest value 7.7% at the composition of EG/pencil-lead =1:1.
► This is a first report to the application of expanded graphite in DSSCs.