The Role of π Bridges in High‐Efficiency DSCs Based on Unsymmetrical Squaraines. Issue 5 (18th December 2012)

• Record Type: Journal Article
• Authors: Delcamp, Jared H.; Shi, Yanrong; Yum, Jun‐Ho; Sajoto, Tissa; Dell'Orto, Elisa; Barlow, Stephen; Nazeeruddin, Mohammad K.; Marder, Seth R.; Grätzel, Michael
• Is Part Of: Chemistry. Volume 19:Issue 5(2013)
• Page Start: 1819
• Page End: 1827
• Publication Date: 2012-12-18
• Subjects: Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.201202677
• Languages: English
• ISSNs: 0947-6539

Abstract

<abstract abstract-type="main" xml:lang="en"> <title>Abstract</title> <p>A series of squaraine‐based sensitizers with various π bridges and anchors were prepared and examined in dye‐sensitized solar cells. The carboxylic anchor group was attached onto a squaraine dye through π bridges with and without an ethynyl spacer. DFT studies indicate that the LUMO is delocalized throughout the dyes, whilst the HOMO resides on the squaraine core. The dye that incorporates a 4, 4‐di‐<italic>n</italic>‐hexyl‐cyclopentadithiophene group that is directly attached onto the π bridge, <bold>JD10</bold>, exhibits the highest power conversion efficiency in a DSC; this result is attributed, in part, to the deaggregative properties that are associated with the <italic>gem</italic>‐di‐<italic>n</italic>‐hexyl substituents, which extend above and below the π‐conjugated dye plane. Dye <bold>JD10</bold> demonstrates a power‐conversion efficiency of 7.3 % for liquid‐electrolyte dye‐sensitized solar cells and 7.9 % for cells that are co‐sensitized by another metal‐free dye, <bold>D35</bold>, which substantially exceed the performance of any previously tested squaraine sensitizer. A panchromatic incident‐photon‐to‐current‐conversion efficiency curve is realized for this dye with an excellent short‐circuit current of 18.0 mA cm<sup>−2</sup>. This current is higher than that seen for other squaraine dyes, partially owing to a high molar absorptivity of >5 000 <sc>M</sc><sup>−1</sup> cm<sup>−1</sup> from 400 nm to the long‐wavelength onset of 724 nm for dye <bold>JD10</bold>.</p> </abstract>