Elimination of 50% Iodine and Excellent Performance of Dye-Sensitized Solar Cell Enabled by TEMPO Radical Dendrimer–Iodide Dual Redox Systems

Abstract

Detrimental effect of counter electrode corrosion, electrolyte leakage problem, and sublimation of iodine ions affect the performance and stability of dye-sensitized solar cells (DSSCs) based on a liquid redox electrolyte system. TEMPO/TEMPO + is the most desirable one to replace the existing redox couples in liquid electrolyte owing to its rapid and reversible one electron kinetics, high diffusion coefficient, and electrochemical stability. In the present study, a fifth generation polyurethane dendrimer end-capped with 2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPO) was prepared and employed as an active redox mediator to replace up to 75% of iodine ions in the standard liquid iodide electrolyte system to elucidate the effect of a quick selfexchange reaction in DSSCs. In this concern, quasi-gel type electrolytes were prepared by incorporating different amounts of a newly prepared TEMPO radical dendrimer to a liquid I − /I 3 − redox system and were used as a dual redox mediator for DSSCs. Blending of 50 wt % of I − /I 3 − electrolyte with 50 wt % of the radical dendrimer improved the device performance (η) unprecedentedly from 6.56 to 9.54% upon illumination with 1 sun intensity. Thorough electrochemical characterization of cells was carried out and all such parameters authenticated this remarkable enhancement. Stability of the device was also found to be good, which retained its >80% efficiency after 30 days.

Effect of Interfacial Polarization on the Trap Passivation and Dielectric Constant of SrF2/TiO2 for Dye-Sensitized Solar Cells

“…It can balance the tri-iodide generation/recombination and the charge transport at the Pt/electrolyte interface. However, an increase in the volume fraction of SrF 2 to 20 and 30 wt % reduced the dye loading of the photoanode and decreased the dye excitation as well as the tri-iodide generation in the electrolyte. − The low dye loading of the SrF 2 /TiO 2 hybrid photoanode leads to reduced dye excitation/charge separation, and the reduction process at the Pt/electrolyte interface gets suppressed. , This was the prospective reason for the high R ct for the SrF 2 /TiO 2 ( %w/w 20/80)-DSSC and SrF 2 /TiO 2 ( %w/w 30/70)-DSSC. The obtained low R ct of control-DSSC and SrF 2 /TiO 2 ( %w/w 10/90)-DSSC was in accordance with the estimated shorter charge transport lifetime (τ t ) of 47.82 and 47.46 μs, respectively.…”

“…37−40 The low dye loading of the SrF 2 /TiO 2 hybrid photoanode leads to reduced dye excitation/charge separation, and the reduction process at the Pt/electrolyte interface gets suppressed. 41,42 This was the prospective reason for the high R ct for the SrF 2 /TiO 2 (%w/w 20/80)-DSSC and SrF 2 /TiO 2 (%w/w 30/70)-DSSC. The obtained low R ct of control-DSSC and SrF 2 /TiO 2 (%w/w 10/90)-DSSC was in accordance with the estimated shorter charge transport lifetime (τ t ) of 47.82 and 47.46 μs, respectively.…”

Review on Functional Electrolyte, Redox Polymers, and Solar Conversions in 3G Emerging Photovoltaic Technologies: Progress and Outlook

“…The redox centers (electrolyte group), i.e., TEMPO, can be oxidized and reduced reversibly to play a dual role with the redox mediator. 62 The photovoltaic efficiency can be surged by calibrating the redox structure and corresponding potential of electrolyte. In general, relatively high redox potential yields a lower value of photovoltage, which is of course due to an unwanted side reaction at the interface of photoanode and electrolyte.…”

“…Photovoltaic redox reaction imparts electrons to the oxidized photosensitizer and accepts electrons from cathode. The redox centers (electrolyte group), i.e., TEMPO, can be oxidized and reduced reversibly to play a dual role with the redox mediator . The photovoltaic efficiency can be surged by calibrating the redox structure and corresponding potential of electrolyte.…”

Remarkable 8.3% efficiency and extended electron lifetime towards highly stable semi-transparent iodine-free DSSCs by mitigating the in-situ triiodide generation

“…The different I2 concentrations in electrolytes influence the charge transportation and electron recombination dynamics in DSSCs [53]. Ali et al [54] showed that the removal of 50% of I2 from the QSSCs significantly improved both the stability and the PCE of DSSCs. The first I2-free DSSC was reported by Wang et al [55] with a PCE of 5.5%, maintaining about 70% of its initial photonic efficiency after one-month storage.…”