Highly efficient dye-sensitized solar cells achieved through using Pt-free Nb sub(2)O sub(5)/C composite counter electrode and iodide-free redox couples

• Published in: Journal of power sources 2016-03, Vol.308, p.37-43
• Main Authors: Lia, Ling, Lua, Qi, Lib, Wenyan, Lia, Xiaowei, Hagfeldtc, Anders, Zhanga, Wenming, Wub, Mingxing
• Format: Article
• Language: English
• Subjects: Carbon-carbon composites; Catalytic activity; Couples; Electrodes; Particulate composites; Photovoltaic cells; Platinum; Solar cells
• ISSN: 0378-7753
• DOI: 10.1016/j.jpowsour.2016.01.053

To improve the catalytic activity of Nb sub(2)O sub(5), a composite Nb sub(2)O sub(5)/C (Nb sub(2)O sub(5) imbedded in carbon support) is synthesized with a simple in situ method and then introduced the composite into dye-sensitized solar cells (DSCs) as a counter electrode (CE) catalyst. Based on the analysis of the cyclic voltammetry, electrochemical impedance spectroscopy, and Tafel-polarization curve measurements, the catalytic activity of the Nb sub(2)O sub(5)/C composite for the regeneration of iodide-free redox couples of polysulfide (T sub(2)/T super(-)) and cobalt complex (Co super(3+/2+)) is indeed enhanced significantly as compared with pure Nb sub(2)O sub(5), because the composite electrode eliminates the particle aggregation and forms a mesoporous network structure with large pore size. The T sub(2)/T super(-) electrolyte based DSCs with Nb sub(2)O sub(5)/C CE yields a high power conversion efficiency (PCE) of 6.11%, generating a great improvement of 63.8% as compared to the Pt CE based DSCs. In addition, the Nb sub(2)O sub(5)/C exhibits higher catalytic activity than Pt for regenerating the Co super(3+/2+) redox couple and the DSCs using Nb sub(2)O sub(5)/C CE shows a high PCE of 9.86%.