Organic Dyes with Well-Defined Structures for Highly Efficient Dye-Sensitised Solar Cells Based on a Cobalt Electrolyte

• Published in: Chemistry : a European journal Vol. 21; no. 42; pp. 14804 - 14811
• Main Authors: Seo, Kang Deuk, Choi, In Tack, Kim, Hwan Kyu
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 12-10-2015; WILEY‐VCH Verlag; Wiley Subscription Services, Inc
• Subjects: Anchoring; benzothiadiazole; bisdimethylfluorenylamine; Chemistry; Density; dye-sensitised solar cell; Dyes; dyes/pigments; Molecular structure; organic dye; Photoelectric effect; Photovoltaic cells; Solar cells; Solar energy; Thiophenes; dyes/pigments; bisdimethylfluorenylamine; thiophenes; benzothiadiazole; dye-sensitised solar cell; organic dye
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.201502289

Seven SGT organics dyes, containing bis‐dimethylfluoreneyl amino groups with a dialkoxyphenyl unit as an electron donor and a cyanoacrylic acid group as an anchoring group, connected with oligothiophenes, fused thiophenes and benzothiadiazoles as π‐bridges, were designed and synthesised for applications in dye‐sensitised solar cells (DSSCs). The photovoltaic performance of DSSCs based on organic dyes with oligothiophenes depends on the molecular structure of the dyes, in terms of the length change of the π‐bridging units. The best performance was found with a π‐bridge length of about 6 Å. To further enhance the photovoltaic performance associated with this concept, cyclopenta[1,2‐b:5,4‐b′]dithiophene (CPDT) and benzothiadiazole were introduced into the π‐bridge unit. As a result, the DSSC based on the organic dye containing the CPDT moiety showed the best photovoltaic performance with a short‐circuit photocurrent density (Jsc) of 14.1 mA cm−2, an open‐circuit voltage (Voc) of 0.84 V and a fill factor (FF) of 0.72, corresponding to an overall conversion efficiency (η) of 8.61 % under standard AM 1.5 irradiation.
How long is the ideal bridge? The photovoltaic performance of DSSCs based on organic dyes with oligothiophenes depends on the molecular structure of the dyes in terms of the length of the π‐bridge. The organic dyes, consist of bisdimethylfluoreneyl amino groups with a dialkoxyphenyl unit as the electron donor and a cyanoacrylic acid group as an anchoring group, and are connected to oligothiophenes, fused thiophenes and electron‐withdrawing benzothiadiazoles as π‐bridging units (an example is shown here).