Gram-Scale Synthesis of Catalytic Co S Nanocrystal Ink as a Cathode Material for Spray-Deposited, Large-Area Dye-Sensitized Solar Cells

We report the development of Co9S8 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 Co9S8 nanoaystal Is carried out via a noninjection reaction by mixing anhydrous CoCl2 with trioctylphosphine (TOP), dodecanethiol and oleylamine (OLA) at 250 degrees C The Co9S8 nanoaystals possess excellent catalytic ability with respect to I-/I-3(-) redox reactions. The Co9S8 nanocrystals are prepared as nanoinks to fabricate uniform, crack-free Co9S8 thin films on different substrates by using a spray deposition technique. These OA films are used as counter electrodes assembled with dye-adsorbed TiO2 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 Pa 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.