Efficiency enhancement in dye sensitized solar cells using gel polymer electrolytes based on a tetrahexylammonium iodide and MgI2 binary iodide system

Abstract

Quasi-solid-state dye-sensitized solar cells have drawn the attention of scientists and technologists as a potential candidate to supplement future energy needs. The conduction of iodide ions in quasi-solid-state polymer electrolytes and the performance of dye sensitized solar cells containing such electrolytes can be enhanced by incorporating iodides having appropriate cations. Gel-type electrolytes, based on PAN host polymers and mixture of salts tetrahexylammonium iodide (Hex4N(+)I(-)) and MgI2, were prepared by incorporating ethylene carbonate and propylene carbonate as plasticizers. The salt composition in the binary mixture was varied in order to optimize the performance of solar cells. The electrolyte containing 120% Hex4N(+)I(-) with respect to weight of PAN and without MgI2 showed the highest conductivity out of the compositions studied, 2.5 × 10(-3) S cm(-1) at 25 °C, and a glass transition at -102.4 °C. However, the electrolyte containing 100% Hex4N(+)I(-) and 20% MgI2 showed the best solar cell performance highlighting the influence of the cation on the performance of the cell. The predominantly ionic behaviour of the electrolytes was established from the dc polarization data and all the electrolytes exhibit iodide ion transport. Seven different solar cells were fabricated employing different electrolyte compositions. The best cell using the electrolyte with 100% Hex4N(+)I(-) and 20% MgI2 with respect to PAN weight showed 3.5% energy conversion efficiency and 8.6 mA cm(-2) short circuit current density.

Dependence of solar cell performance on the nature of alkaline counterion in gel polymer electrolytes containing binary iodides

“…In order to improve the solar cell performance by using mutually competing effects of small and large size cations in the electrolyte, mixed cation-iodide salt containing electrolyte systems has been investigated recently [20][21][22]. The general observation has been that larger cations improve the V oc in the cell, whereas the smaller cations improve the J sc .…”

“…However, due to the complex nature of polymer electrolytes and due to many different competing effects that influence the mass transport in such electrolytes, a careful investigation is needed in order to understand the behavior of these binary salt systems. The cation effect of binary iodide (tetrahexylammonium iodide and MgI 2 )-based quasi-solid dye-sensitized PECSCs was investigated using plasticized PAN-based electrolyte [21]. The electrolyte-containing salt weight ratio Hex 4 NI to MgI 2 100:20 has shown the best solar cell performance highlighting the influence of the binary cations on the performance improvement of the cell.…”

N719 and N3 dyes for quasi-solid state dye sensitized solar cells - A comparative study using polyacrylonitrile and CsI based electrolytes

“…However, the conductivity variation with temperature observed in this work can be attributed to VTF (Vogel-Tammann-Fulcher) nature rather than Arrhenius nature (Figure 4). In general, the VTF behavior is common for this kind of gel polymer electrolytes (Bandara et al, 2012). Table 2.…”

“…A series of electrolytes were prepared by adding relevant amounts of Pr 4 NI (0.0443 g), MPII (0.0126 g), 4-tert-butylpyridine (4TBP) to the (PAN) 10 (EC) 25 (PC) 20 (CsI) 1.2 (I 2 ) 0.12 electrolyte as given in Table 1. Gel polymer electrolytes were prepared using the method already described in a previous report (Bandara et al, 2012). …”

“…The chemical and physical instability issues, mainly originating from the volatile liquid electrolyte used in DSSCs, are the primary disadvantages for their Ceylon Journal of Science 45(2) 2016: 61-69 DOI: http://doi.org/10.4038/cjs.v45i2.7389 RESEARCH ARTICLE utilization as a long term, stable, outdoor applications (Bella and Bongiovanni, 2013). However, the instability issues can be resolved to a certain extent through the replacement of liquid electrolytes by gel or solid polymer electrolytes, which do not use volatile solvents (Huo et al, 2007;Bandara et al, 2012). Still, the cell efficiency suffers due to resistive losses originated by poor ionic conductivity in such electrolytes.…”