A high-performance counter electrode based on poly(3,4-alkylenedioxythiophene) for dye-sensitized solar cells

A poly(3,3-diethyl-3,4-dihydro-2H-thieno-[3,4-b][1,4]dioxepine) (PProDOT-Et-2) counter electrode prepared by electrochemical polymerization on a fluorine-doped tin oxide (FTO) glass substrate was incorporated in a platinum-free dye-sensitized solar cell (DSSC). The surface toughness and I-/I-3(-) redox reaction behaviors based on PProDOT-Et-2, poly(3,4-propylenedioxythiophene) (PProDOT), poly(3,4-ethylenedioxythiophene) (PEDOT), and sputtered-Pt electrodes were characterized, and their performances as counter electrodes in DSSCs were compared. Cells fabricated with a PProDOT-Et-2 Counter electrode showed a higher conversion efficiency of 7.88% compared to cells fabricated with PEDOT (3.93%), PProDOT (7.08%), and sputtered-Pt (7.77%) electrodes. This enhancement was attributed to increases in the effective Surface area and good catalytic properties for I-3 reduction. In terms of the film thickness effect, the fill factor was strongly dependent on the deposition charge capacity of the PProDOT-Et-2 layer, but the aggregation of PProDOT-Et-2 in thicker layers (>80 mC cm(-2)) resulted in decreases in J(SC) and the cell conversion efficiency, The charge transfer resistances (R-ct1) of the PProDOT-Et-2 counter electrodes had the lowest value of similar to 18 Omega at a deposition charge capacity of 40 mC cm(-2). These results indicate that films with high conductivity, high active surface area, and good catalytic properties for I-3(-) reduction can potentially be used as the Counter electrode in a high-performance DSSC. (C) 2008 Elsevier B.V. All rights reserved.