Co-sensitization promoted light harvesting for organic dye-sensitized solar cells using unsymmetrical squaraine dye and novel pyrenoimidazole-based dye

The pure organic dyes are investigated recently because of its high extinction coefficient and relatively low cost. In order to enhance the performance of the organic dyes, co-sensitization strategy is applied. The co-sensitization by the absorption of SQ2/5c shows enhanced photovoltaic performance for the pertinent DSSCs, which leads to a broader light harvesting window (400-750 nm) and a higher overall efficiency of 6.24% while the performances of DSSCs with the individual dyes are 5.33% (Sc) and 3.98% (SQ2), respectively. Furthermore, the overall efficiency can be further improved to 6.71% with the incorporation of chenodeoxycholic acid (CDCA). In addition, the incident photon-to-current conversion efficiency (IPCE) and UV-visible absorption spectra are also used to explain and support the behavior of the co-sensitized solar cells. The investigation of the long-term stability of the DSSC based on co-sensitization of SQ2/5c dyes with the use of binary ionic liquid is performed. The DSSC with the co-sensitization strategy possesses an unfailing durability up to 1000 h. (C) 2013 Elsevier B.V. All rights reserved.