Novel one pot stoichiometric synthesis of nickel sulfide nanomaterials as counter electrodes for QDSSCs
Solution combustion synthesis has been used for the first time to synthesize metal sulfide nanomaterials. Selective stoichiometric synthesis of nickel sulfide nanomaterials was achieved in a single step by using combustion synthesis under ambient conditions and the samples were tested as counter electrodes in a typical quantum dot sensitized solar cell (QDSSC). By varying the oxidant/fuel ratio, different stoichiometric nickel sulfide nanomaterials were obtained. Interestingly, a maximum of fourfold increase in efficiency (1.1%) was achieved with nickel sulfide counter electrode when compared to the Pt counter electrode (0.25%). This can be attributed to the less charge transfer resistance offered by nickel sulfide samples compared to Pt, which was confirmed by electrochemical impedance spectroscopy. Among different stoichiometric compositions of nickel sulfide, Ni3S2 was found to exhibit the least charge transfer resistance and superior solar cell efficiency. The present study describes a novel selective stoichiometric synthetic approach and facile fabrication procedure for low cost counter electrode materials in QDSSCs. (C) 2014 Elsevier B.V. All rights reserved.