Cation Exchange at Semiconducting Oxide Surfaces: Origin of Light-Induced Performance Increases in Porphyrin Dye-Sensitized Solar Cells

Abstract

The origin of simultaneous improvements in the short-circuit current density ( Jsc) and open-circuit voltage (Voc) of porphyrin dye-sensitized TiO2 solar cells following white light illumination was studied by systematic variation of several different device parameters. Reduction of the dye surface loading resulted in greater relative performance enhancements, suggesting open space at the TiO2 surface expedites the process. Variation of the electrolyte composition and subsequent analysis of the conduction band potential shifts suggested that a light-induced replacement of surface-adsorbed lithium (Li+) ions with dimethylpropylimidazolium (DMPIm+) ions was responsible for an increased electron lifetime by decreasing the recombination with the redox mediator. Variation of the solvent viscosity was found to affect the illumination time required to generate increased performance, while similar performance enhancements were not replicated by application of negative bias under dark conditions, indicating the light exposure effect was initiated by formation of dye cation molecules following photoexcitation. The substituents and linker group on the porphyrin chromophore were both varied, with light exposure producing increased electron lifetime and Voc for all dyes; however, increased Jsc values were only measured for dyes containing binding moieties with multiple carboxylic acids. It was proposed that the initial injection limitation and/or fast recombination process in these dyes arises from the presence of lithium at the surface, and the improved injection and/or retardation of fast recombination after light exposure is caused by the Li+ removal by cation exchange under illumination. there an initial injection limitation and/or fast recombination process in these dyes arises from the presence of lithium at the surface, and the improved injection and/or retardation of fast recombination after light exposure was caused by the Li + removal by cation exchange under illumination.

Structural Effect of the Pendant Unit in Thiocyanate‐Free RuII Sensitizers on the Dye‐Sensitized Solar Cell Performance

“…We are aware that some papers have shown different E cb values with different dyes. We suppose that the apparent difference is due to the effect of electrolytes . Since we used the same electrolyte solution, we assume that the values of E cb for the DSSCs/ T11 and T12 are the same.…”

Printable Organic Semiconductors for Radiation Detection: From Fundamentals to Fabrication and Functionality

“…This emulsion method provides nanoparticulate OSC inks that are stable over time periods of months to years. Nanoparticles of OSCs synthesized via the miniemulsion method encompass various morphologies, including pristine pure semiconductors [84,91,92], core-shell combinations of two semiconductors [23,[93][94][95][96][97], and highly intermixed blends of two semiconductors [8,98]. This morphology has been shown to be tuneable and highly dependent on the relative surface energies of the two materials [99].…”

“…OSC materials offer the exciting prospect of combining the electronic advantages of semiconducting substrates with the chemical and mechanical benefits of organic compounds such as plastics. The suitability of OSC materials for this purpose arises from the ability to easily modify their chemical, physical, and electronic properties and control their film-forming mechanisms through conventional wet chemistry [8]. Furthermore, because these materials are composed almost entirely of carbon, hydrogen, and oxygen, they have a response to radiation that closely mimics that of water, thus providing a key advantage for radiation dosimetry [9,10].…”

Light soaking effect driven in porphyrin dye-sensitized solar cells using 1D TiO2 nanotube photoanodes

“…−1 ) as a counter electrode separated by a sealant (Surlyn 60 μm thickness, Solaronix). The electrolyte was a mixture of 0.1 M LiI, 0.6 M 1, 2dimethyl-3-propylimidazoliumiodide (DMPImI), 0.03 M I 2 and 0.5 M t-butylpyridine (tBP) in acetonitrile [31]. The electrolyte was injected to the cell through a hole drilled through the counter electrode with the aid of a vacuum.…”