Quantification of Dyes Generating Photocurrent and/or Photoluminescence in Dye-Sensitized Solar Cells Using Laser Scanning Microscopy

Masaaki Mitsui, Kyosuke Mori and Reina Kobayashi
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Masaaki Mitsui: Department of Chemistry, College of Science, Rikkyo University, 3-34-1, Nishiikebukuro, Toshima-ku, Tokyo 171-8501, Japan
Kyosuke Mori: Department of Chemistry, College of Science, Rikkyo University, 3-34-1, Nishiikebukuro, Toshima-ku, Tokyo 171-8501, Japan
Reina Kobayashi: Department of Chemistry, College of Science, Rikkyo University, 3-34-1, Nishiikebukuro, Toshima-ku, Tokyo 171-8501, Japan

Energies, 2020, vol. 13, issue 8, 1-12

Abstract: Photoconversion processes such as electron injection (photooxidation) and dye regeneration (reduction) in dye-sensitized solar cells (DSSCs) occur at considerably inhomogeneous semiconductor/dye/electrolyte interfaces, implying a very high heterogeneity of interfacial photoconversion kinetics. Herein, we present a temporally and spatially resolved investigation of DSSCs comprising a cover glass photoanode with a 100-nm thick TiO 2 layer loaded with the metal-free organic dye sensitizer MK-2, which is performed by employing laser scanning microscopy (LSM) for the simultaneous measurement of the photocurrent (PC) and photoluminescence (PL) of DSSCs under short-circuit conditions. Analysis of PL decay curves and the excitation rate dependences of PC and PL obtained for local (or submicrometric) areas of the MK-2-DSSC allows disclosing and quantifying three types of dyes coexisting in the DSSCs: (i) a dye that only generates PC (“PC-dye,” 75% of total dye molecules in the DSSC), (ii) a dye that generates both PC and PL (“PCPL-dye,” 20%), and (iii) a dye that only generates PL (“PL-dye,” 5%). Considering recent theoretical reports on cyanoacrylic dyes, we propose that the PC-dye and the PCPL-dye are covalently bound on a TiO 2 surface with different adsorption modes (presumably bidentate and tridentate bridging configurations), whereas the PL-dye is noncovalently trapped within a mesoporous TiO 2 film.

Keywords: dye-sensitized solar cells; photocurrent; photoluminescence; microscopy (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2020
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