Journal
ACS SUSTAINABLE CHEMISTRY & ENGINEERING
Volume 9, Issue 15, Pages 5252-5259Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acssuschemeng.0c08195
Keywords
copper redox helicates; electron recombination; mononuclear; binuclear; dye-sensitized solar cells
Categories
Funding
- National Natural Science Foundation of China [51661135021, U1710117]
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Redox mediators are crucial in dye-sensitized solar cells, and copper complexes are a good option, despite electron recombination issues. By synthesizing two helical copper(I) complexes and eliminating the use of 4-(tert-butyl)pyridine, the efficiency of the solar cells was improved. Increasing the concentration of (CuLa)-La-I showed an increase in both photocurrent and photovoltage, leading to the best power conversion efficiency at 8.2%. Further investigation into the relationship between Cu(I) concentration and recombination was conducted for future research.
Redox mediators play a major role in determining the photocurrent and photovoltage in dye-sensitized solar cells (DSSCs). Copper complexes are a good option for redox mediators but suffer from electron recombination. The traditional method is to add 4-(tert-butyl)pyridine (TBP) to the electrolyte, which is coordinated with the empty orbit of Ti, thereby slowing down the oxidized mediator's ability to capture electrons. However, this strategy will result in competitive coordination between the redox mediator and TBP, decreasing the stability of the device. In this study, two helical copper(I) complexes are synthesized and applied to TBP-free solar cells. La (1,3-bis(2,2'-bipyridin-6-yloxy)propane) and Lb (1,3-bis[(6'-methyl-2,2'-bipyridin-6-yl)oxy]propane) tend to form double-stranded helicates ([Cu-2(Ln)(2)](2+), n = a, b) rather than mononuclear complexes ([Cu(Ln)](+), n = a, b). To facilitate quantitative analysis of the complexes, Cu(I)Ln and Cu(II)Ln (n = a, b) are used as molecular formulae. (CuLa)-La-I and Cu(I)Lb are characterized by electrospray mass spectroscopy, H-1 NMR spectroscopy, and electrochemistry. J-V measurement shows that both V-oc and J(sc) increase with the increase of (CuLa)-La-I concentration (below 0.1 M), and the best power conversion efficiency is 8.2%. The relationship between Cu(I) concentration and recombination for further study was measured by IMVS.
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