Among the new photovoltaic technologies, the Dye-Sensitized Solar Cell (DSC) is becoming a realistic approach towards energy markets such as BIPV (Building Integrated PhotoVoltaics). In order to improve the performances of DSCs and to increase their commercial attractiveness, cheap, colourful, stable and highly efficient ruthenium-free dyes must be developed. Here we report the synthesis and complete characterization of a new purely organic sensitizer (RK1) that can be prepared and synthetically upscaled rapidly. Solar cells containing this orange dye show a power conversion efficiency of 10.2% under standard conditions (AM 1.5G, 1000 Wm−2) using iodine/iodide as the electrolyte redox shuttle in the electrolyte, which is among the few examples of DSC using an organic dyes and iodine/iodide red/ox pair to overcome the 10% efficiency barrier. We demonstrate that the combination of this dye with an ionic liquid electrolyte allows the fabrication of solar cells that show power conversion efficiencies of up to 7.36% that are highly stable with no measurable degradation of initial performances after 2200 h of light soaking at 65°C under standard irradiation conditions. RK1 achieves one of the best output power conversion efficiencies for a solar cell based on the iodine/iodide electrolyte, combining high efficiency and outstanding stability.
Two new D-p-A type organic sensitizers, MP124 and MP-I-50, were synthesized and their electrochemical and spectroscopic properties studied. Efficiencies of DSSC devices utilizing these dyes were also investigated, where sensitization solvent, sensitization time and additive concentration were all varied. Under standard AM 1.5G simulated solar radiation, optimized MP124 devices show an efficiency of 7.45% (V oc ¼ 0.73 V; J sc ¼ 14.44 mA cm À2 ; FF ¼ 70%) while optimized MP-I-50 devices show an efficiency of 5.66% (V oc ¼ 0.68 V; J sc ¼ 12.06 mA cm À2 ; FF ¼ 69%). Transient absorption spectroscopy studies show that regeneration of dye cations by the red-ox electrolyte was more efficient in MP124 cells which is attributed to its higher HOMO energy leading to greater driving force for the regeneration reaction. Transient photovoltage studies showed that electron lifetimes were longer lived in MP124 explaining the higher V oc for these cells compared to MP-I-50 cells. DFT and MP2 calculations indicate that this is due to the greater tendency of MP-I-50 to form charge-transfer complexes with the I 2 species in the electrolyte, due to the presence of an additional EDOT in its structure compared to MP124. This work highlights the effect that small changes to the sensitizer structure can have on the interfacial charge transfer reactions and ultimately on the device efficiency.
A working electrode design based on a highly porous 1D photonic crystal structure that opens the path towards high photocurrents in thin, transparent, dye‐sensitized solar cells is presented. By enlarging the average pore size with respect to previous photonic crystal designs, the new working electrode not only increases the device photocurrent, as predicted by theoretical models, but also allows the observation of an unprecedented boost of the cell photovoltage, which can be attributed to structural modifications caused during the integration of the photonic crystal. These synergic effects yield conversion efficiencies of around 3.5% by using just 2 μm thick electrodes, with enhancements between 100% and 150% with respect to reference cells of the same thickness.
A novel family of six donor-acceptor type organic sensitizers for dye-sensitized solar cells (DSSCs) is reported. The dyes have been designed to have outstanding light absorption properties in the visible range and being able to achieve high photon-to-electrical current conversion for BIPV (building-integrated photovoltaic). Moreover, stability tests under illumination at 1 Sun and 65 1C showed a great stability for some of the devices, with less than 6% decrease of power conversion efficiency after 3000 hours. The differences in the performance of the six sensitizers under standard illumination conditions can be correlated with the observed differences in the photo-induced transient photovoltage and in charge extraction measurements. We report the use of one of the dyes for the fabrication of semi-transparent solar modules showing an active area of 1400 cm 2 and a power output of 10.5 W m -2 . Broader contextTremendous progress has been achieved in the past decade in the effciency of dye-sensitized mesoscopic solar cells (DSSC), owing to the development of new metal-free organic sensitizers. To increase their commercial attractiveness and to make them a realistic approach towards energy markets such as BIPV (building integrated photovoltaics), the new dyes must be cheap, colorful, and effcient, and moreover they must show a high stability. In this paper, we report a family of donor-acceptor type metal-free photosensitizers with simple structures for DSSCs. The precise molecular design of the dyes leads to a quite narrow light absorption in the visible range and a high photon-to-electrical current conversion in solar cells. These organic sensitizers that can be prepared in few steps show power efficiencies over 10% when they are used with iodine-based liquid electrolytes. Stability tests and fabrication of semitransparent solar modules with an active area of 1400 cm 2 demonstrate the potential of these organic dyes for large scale applications and mass production for BIPV.
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