Abstract
We report the development of Co 9 S 8 nanocrystals as a cost-effective cathode material that can be readily combined with spraying techniques to fabricate large-area dye-sensitized solar cell (DSSC) devices and can be further connected with series or parallel cell architectures to obtain a relatively high output voltage or current. A gram-scale synthesis of Co 9 S 8 nanocrystal is carried out via a noninjection reaction by mixing anhydrous CoCl 2 with trioctylphosphine (TOP), dodecanethiol and oleylamine (OLA) at 250 C. The Co 9 S 8 nanocrystals possess excellent catalytic ability with respect to I - /I 3 - redox reactions. The Co 9 S 8 nanocrystals are prepared as nanoinks to fabricate uniform, crack-free Co 9 S 8 thin films on different substrates by using a spray deposition technique. These Co 9 S 8 films are used as counter electrodes assembled with dye-adsorbed TiO 2 photoanodes to fabricate DSSC devices having a working area of 2 cm 2 and an average power conversion efficiency (PCE) of 7.02 ± 0.18% under AM 1.5 solar illumination, which is comparable with the PCE of 7.2 ± 0.12% obtained using a Pt cathode. Furthermore, six 2 cm 2 -sized DSSC devices connected in series output an open-circuit voltage of 4.2 V that can power a wide range of electronic devices such as LED arrays and can charge commercial lithium ion batteries. © 2013 American Chemical Society.