Gel polymer electrolyte containing cobalt redox mediator for application in dye-sensitized solar cells

Author(s)

Gabriela Gava Sonai

• Document type: Doctoral Thesis
• Press: Campinas, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Instituto de Química
• Defense date: 2018-03-14

Examining board members

Ana Flávia Nogueira; Cláudia Longo; Pablo Sebastián Fernández; Carlos Frederico de Oliveira Graeff; Glaura Goulart Silva

• Advisor: Ana Flávia Nogueira

Abstract

The long-term stability of dye-sensitized solar cells (DSSCs) is critical for the application of this technology in large scale. In this doctoral thesis, stability studies of DSSCs prepared with redox mediator [Co(bpy)3]2+/3+ using liquid or polymeric gel electrolyte (5% w/w P(EO/EM/AGE) - poly (ethylene oxide-co-2-(2-methoxyethoxy) ethyl glycidyl ether-allyl glycidyl ether) were investigated. In the first part of this thesis, the DSSCs were sensitized with an organic dye, MK2 (2-cyano-3-[5.-(9-ethyl-9H-carbazol-3-yl)- 3¡Ç,3¡È,3.,4-tetra-n-hexyl-[2,2¡Ç,5¡Ç,2¡È,5¡È,2.]-quarter thiophen-5- yl] acrylic acid) or ruthenium (II) based dye Z907 (cis-bis(isothiocyanato)(2,2¡¯-bipyridyl-4,4¡¯- dicarboxylato)(4,4¡¯-di-nonyl-2¡¯-bipyridyl)ruthenium(II)). The device¡¯s stability was tested under visible light. At the end of 1000 h, the Z907 cells containing liquid and gel electrolyte presented similar behavior with efficiency values of ¥ç=3.7%¡¾0.7 and ¥ç=3.3%¡¾0.4, respectively. The MK2 cells with liquid electrolyte maintained 83% of the initial efficiency value, while the gel electrolyte devices retained 60%. The diffusion limited transport of the Co3+ species was one factor that led to a drop in performance for the gel electrolyte devices. We found out that the nature of the dye influences the long-term stability of DSSCs, especially for devices sensitized with the MK2 dye containing polymeric gel electrolyte. In the second part of this work, stability tests were carried out in the devices for 110 h under UV radiation using two UV protection approaches: UV filter at the top of the device and a benzophenone based additive into the electrolyte; in addition to a combination of both methods. The DSSCs were prepared with the MK2 dye and the [Co(bpy)3]2+/3+ mediator for liquid electrolyte. The gel polymer electrolyte was prepared by addition of 5%(w/w) of P(EO/EM/AGE) and benzophenone additive. The UV filter under the top of the device was more efficient in preventing degradation than the BZF additive in the electrolyte (AU)

• FAPESP's process: 13/18106-0 - Solid and quasi-solids polymer electrolytes containing alternatives redox couples to the iodide/triiodide for use in dye sensitized solar cells.
• Grantee: Gabriela Gava Sonai
• Support Opportunities: Scholarships in Brazil - Doctorate