We report a series of ‘donor-free’ dyes, featuring moieties of oligo(4,4-dihexyl-4H-cyclopenta[1,2-b:5,4-b’]dithiophene) (CPDT) functionalized with cyanoacrylic end groups for mesoscopic titania solar cells based on I-/I3- or Co(II)/Co(III) redox couple and spiro-OMeTAD hole transporter. These were compared with similar cells using an oligo(3-hexylthiophene) dye (5T) which we have reported before. Extending the CPDT moiety of the dye molecules from one to three (denoted as CPDT-1, CPDT-2 and CPDT-3) widens the photoresponse overlap with the solar spectrum, increases the molar absorption coefficient up to 75000 M-1cm-1 and improves the short-circuit current (JSC), open-circuit voltage (VOC) and power conversion efficiency (PCE) for all types of DSSCs. Among these sensitisers, CPDT-3 shows the highest PCE of 6.7%, 7.3% and 3.9% with I-/I3-, Co(II)/Co(III) redox couple and spiro-OMeTAD hole transporter, respectively, compared with 7.6%, 9.0% and 4.0% for 5T. Benefiting from the high absorption of CPDT-3, we demonstrate 900 nm-thick mesoporous TiO2 film with remarkable JSC of 10.9 mA cm-2 in solid-state DSCs.
Robertson, Neil. (2016). High Absorption Coefficient Cyclopentadithiophene Donor-free Dyes For Liquid and Solid-state dye-sensitized Solar Cells, [dataset]. University of Edinburgh. School of Chemistry. https://doi.org/10.7488/ds/1410.