Gram-Scale Synthesis of Catalytic Co₉S₈ Nanocrystal Ink as a Cathode Material for Spray-Deposited, Large-Area Dye-Sensitized Solar Cells

Abstract

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 nanocrystal is carried out via a noninjection reaction by mixing anhydrous CoCl2 with trioctylphosphine (TOP), dodecanethiol and oleylamine (OLA) at 250 °C. The Co9S8 nanocrystals possess excellent catalytic ability with respect to I(-)/I3(-) 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 Co9S8 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 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.

High-performance Co9Se8/CoSe counter electrode for dye-sensitized solar cells

“…Co 9 Se 8 /CoSe nanoinks with a concentration of 10 mg ml -1 were obtained with ultrasound for 20 min. The Co 9 Se 8 /CoSe films were formed by spraying the nanoink onto the FTO substrates, which were washed by sonication in acetone, deionized water and ethanol sequentially for 20 min, respectively [19]. The Co 9 Se 8 / CoSe films were sintered at 350°C for 2 h under an Ar atmosphere to obtain Co 9 Se 8 /CoSe CEs.…”

“…After ultrasound for 20 min, Co 9 Se 8 /CoSe nanoinks with a concentration of 10 mg ml -1 are obtained. In order to improve the mechanical strength and conductivity of Co 9 Se 8 /CoSe films, the as-obtained films are sintered under an Ar atmosphere [19]. The Co 9 Se 8 /CoSe films are directly used as CEs of DSSCs.…”

“…In order to reduce the production costs of DSSCs, it is necessary to synthesize the CE with alternative materials. Recently, several kinds of alternative materials with superior performance had been successfully used as CEs in DSSCs, such as carbon materials [12][13][14], conductive polymer materials [15][16][17], and metal chalcogenides [18][19][20][21][22][23][24]. To the best of our knowledge, we known that most of carbon materials and conductive polymer materials had the lower electrocatalytic activity for the reduction of I À 3 , with respective to Pt CE.…”

“…To the best of our knowledge, we known that most of carbon materials and conductive polymer materials had the lower electrocatalytic activity for the reduction of I À 3 , with respective to Pt CE. However, most of metal chalcogenides exhibited a good electrocatalytic activity, due to their distinctive electronic structure and unique physical properties [18][19][20][21][22][23][24]. Among metal chalcogenides, it was interesting to find that graphene-like cobalt selenide structures had the better catalytic activity, resulting from their higher surface area.…”

Hydrothermal growth of MoS2/Co3S4 composites as efficient Pt-free counter electrodes for dye-sensitized solar cells

“…In 2009, Grätzel et al [18] proposed for the first time that CoS nanoparticles, fabricated by electrochemical deposition method, matched the performance of Pt as triiodide reduction catalyst in DSSCs. Besides, Co9S8 nanocrystal inks were employed as cathode materials to fabricate large-area DSSCs combined with spraying techniques, presenting an excellent photovoltaic performance [29]. Carbon-supported Co3S4 nanoparticles, hollow Co3S4 nanoparticles and nanotubes were successfully prepared and the as-obtained materials had an excellent catalytic ability for the oxygen reduction reaction [26].…”