Exploring Deactivation Processes in Organic Dyes Used in Gratzel Cells

Burkhard Zietz^a, Ahmed El-Zohry ^a

^aDepartment of Chemistry

International Conference on Hybrid and Organic Photovoltaics
Proceedings of International Conference on Hybrid and Organic Photovoltaics 2015 (HOPV15)

Roma, Italy, 2015 May 11th - 13th

Organizer: Filippo De Angelis

Poster, Ahmed El-Zohry , 097
Publication date: 5th February 2015

Organic dyes are good candidates to replace dyes based on noble metals, such as N719, in Grätzel cells.¹^,²Organic dyes are characterized by high molar absorptivities, low cost and ease of synthesis on large scales.² Most of these organic dyes are based on the Donor-linker-Acceptor (D-π-A) strategy.² Here, the donor is an electron-rich moiety and the acceptor an electron-deficient one, while the linker is a connecting bridge between them. The acceptor unit has an anchoring group that binds to the semiconductor surface. Upon absorbing light, an intermolecular charge transfer is induced from the donor to the acceptor to reach the conduction band of the semiconductor. Several kinetic pathways are present during this simplified scheme, such as electron injection, electron recombination, and electron regeneration. Recently, we have studied several organic dyes, such as D149, D131, and L0, containing different donor and acceptor moieties,^3-6 and could unravel previously unknown deactivation processes. Among these processes are isomerization³^,⁵, excited state quenching by protons⁴, and an ultrafast twisting process⁶. Based on these findings, we suggest a modified scheme for the synthesis of organic Grätzel cell dyes and expect improved efficiency for these new dyes.

References (1) Liang, M.; Chen, J. Arylamine Organic Dyes for Dye-Sensitized Solar Cells. Chem. Soc. Rev. 2013, 42, 3453. (2) Hagfeldt, A.; Boschloo, G.; Sun, L. C.; Kloo, L.; Pettersson, H. Dye-Sensitized Solar Cells. Chem. Rev. 2010, 110, 6595-6663. (3) El-Zohry, A.; Orthaber, A.; Zietz, B. Isomerization and Aggregation of the Solar Cell Dye D149. J. Phys. Chem. C 2012, 116, 26144-26153. (4) El-Zohry, A. M.; Zietz, B. Concentration and Solvent Effects on the Excited State Dynamics of the Solar Cell Dye D149: The Special Role of Protons. J. Phys. Chem. C 2013, 117, 6544-6553. (5) Zietz, B.; Gabrielsson, E.; Johansson, V.; El-Zohry, A. M.; Sun, L.; Kloo, L. Photoisomerization of the Cyanoacrylic Acid Acceptor Group–a Potential Problem for Organic Dyes in Solar Cells. Phys. Chem. Chem. Phys. 2014, 16, 2251-2255. (6) El-Zohry, A. M.; Roca-Sanjuán, D.; Zietz, B. Ultrafast Twisting of the Indoline Donor Unit Utilized in Solar Cell Dyes: Experimental and Theoretical Studies. J. Phys. Chem. C 2015.DOI: 10.1021/jp505649s.

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