Abstract
Different alkali deep eutectic solvents (DES), such as LiI:nEG, NaI:nEG, and KI:nEG, have been tested as electrolytes for dye sensitized solar cells (DSSCs). These DSSCs were prepared using pure DES or, alternatively, DES combined with different amounts of iodine (I2). The most important parameters, such as open circuit voltage (VOC), short circuit current density (JSC), fill factor (FF), and the overall conversion efficiency (η), were evaluated. Some DES seem to be promising candidates for DSSC applications, since they present higher VOC (up to 140 mV), similar FF values but less current density values, when compared with a reference electrolyte in the same experimental conditions. Additionally, electrochemical impedance spectroscopy (EIS) has been performed to elucidate the charge transfer and transport processes that occur in DSSCs. The values of different resistance (Ω·cm2) phenomena and recombination/relaxation time (s) for each process have been calculated. The best-performance was obtained for DES-based electrolyte, KI:EG (containing 0.5 mol% I2) showing an efficiency of 2.3%. The efficiency of this DES-based electrolyte is comparable to other literature systems, but the device stability is higher (only after seven months the performance of the device drop to 60%).
Highlights
In the past few years, the design of alternative and renewable energy technologies has been considered to be one of the current and most important challenges due to the growth in the energy requirement by the world population demands
The cell assembly is based on the sandwich type of architecture, and the electrolyte is later injected through a hole that was previously made in the cathode
Different parameters should be evaluated to evaluate the deep eutectic solvents (DES) ability to act as intrinsically electrolytes for dye sensitized solar cells (DSSCs): (i) open circuit voltage (VOC ); (ii) short circuit current density (JSC ); and, (iii) fill factor (FF) and the overall conversion efficiency (η) were measured under
Summary
In the past few years, the design of alternative and renewable energy technologies has been considered to be one of the current and most important challenges due to the growth in the energy requirement by the world population demands. Electrons are transported through the mesoporous TiO2 electrode to the cathode through an external circuit, and, used for the reduction of the electrolyte used to re-establish the original state of the dye [5] These devices received much attention, since they display a large flexibility in shape, colour, and transparency, as well as compatibility with flexible substrates, which allows a large variety of designs to facilitate market entry [4,6,7]. Cell lifetime, electrolyte evaporation can occur and, the thermore, photo-anode and cathode (counter electrode, CE), as well as the elecleakage of the cell, negatively affecting the overall performance of the device, mainly its trolyte, are important components in order to obtain higher overall DSSC perforstability over time.
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