Unravel the Impact of Anchoring Groups on the Photovoltaic Performances of Diketopyrrolopyrrole Sensitizers for Dye-Sensitized Solar Cells

• Published in: ACS sustainable chemistry & engineering Vol. 3; no. 10; pp. 2389 - 2396
• Main Authors: Ganesan, Paramaguru, Yella, Aswani, Holcombe, Thomas W, Gao, Peng, Rajalingam, Renganathan, Al-Muhtaseb, Shaheen A, Grätzel, Michael, Nazeeruddin, Mohammad Khaja
• Format: Journal Article
• Language: English
• Published: American Chemical Society 05.10.2015
• Subjects: Dye-sensitized solar cells; Anchoring group; Diketopyrrolopyrrole; Cyanoacrylic acid; TiO2
• ISSN: 2168-0485; 2168-0485
• DOI: 10.1021/acssuschemeng.5b00332

Two D-π-A dyes, one with a strong electron withdrawing cyanoacrylic acid DPP 20 and one with a weak acceptor carboxylic acid DPP 21 have been synthesized and characterized for their application in dye-sensitized solar cells. This allows us to understand the role of electron withdrawing strength of the acceptor anchoring groups on the optoelectronic properties of chromophoric π spacer molecules, e.g., the diketopyrrolopyrrole (DPP) moiety. The low energy absorption maxima of DPP 20 is red-shifted by only 7 nm compared to DPP 21, implying a minimal role for the strong acceptor in the light harvesting properties of colored π spacer molecules. Because of this small red shift, J SC of DPP 20 is marginally higher than that of DPP 21. However, because of the higher fill factor of DPP 21, the overall power conversion efficiency (PCE = 7.65%) is higher than that of DPP20 (7.34%). The data reveal that a weak acceptor is adequate to achieve good light harvesting as well as provide good photovoltaic efficiencies for colored π spacer sensitizers.