A Desirable Hole-Conducting Coadsorbent for Highly Efficient Dye-Sensitized Solar Cells through an Organic Redox Cascade Strategy
✍ Scribed by Dr. Bok Joo Song; Hae Min Song; In Taek Choi; Sang Kyun Kim; Kang Duk Seo; Min Soo Kang; Myung Jun Lee; Dr. Dae Won Cho; Dr. Myung Jong Ju; Prof. Hwan Kyu Kim
- Publisher
- John Wiley and Sons
- Year
- 2011
- Tongue
- English
- Weight
- 689 KB
- Volume
- 17
- Category
- Article
- ISSN
- 0947-6539
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✦ Synopsis
Over the past decade, dye-sensitized solar cells (DSSCs) [1] based on nanocrystalline mesoporous metal oxides (typically TiO 2 ) have been intensively studied and developed as a promising, low-cost alternative to conventional silicon photovoltaic devices. The components of such DSSCs are a dye sensitizer, a TiO 2 metal oxide coated on conductive glass, a redox electrolyte couple, and a counter electrode. As illustrated in Scheme 1, the power-conversion efficiency of DSSCs is strongly dependent upon the minimization of charge recombination losses at the TiO 2 /dye/electrolyte interface (pathways 3 and 4). [2] There are two recombination pathways of importance in DSSCs, in which electrons photoinjected into the TiO 2 electrode can recombine with either dye cations or with redox electrolytes. Moreover, such charge recombination leads to losses in both the short-circuit photocurrent (J sc ) and the open-circuit photovoltage (V oc ), resulting in a decrease in overall energy conversion efficiency (h).
To reduce the possible charge recombination pathways occurring at the TiO 2 /dye/electrolyte interface, several kinds of additives, such as decylphosophonic acid (DPA), dineohexyl bis(3,3-dimethylbutyl)phosphinic acid (DINHOP), and chenodeoxycholic acid (CDCA) have been introduced to adsorb onto the TiO 2 surface. [3] Among them, for example, cholic acid (CA) derivatives as coadsorbents in DSSCs, based on a Ru-pyridyl complex, [4] courmarin, [5] porphyrin, [6] phthalocyanine, [7] and naphthalocyanine dye, [8] have been investigated well. Deoxycholic acid (DCA) is often used as a coadsorbent to break up organic and Ru-dye aggregates and hence to significantly improve V oc and J sc . [5,9] Moreover, alternative approaches directed toward the minimization of recombination losses have been extensively studied by not only the insertion of a metal oxide blocking layer, [10] but also by energetic cascades for multistep hole conductors (HC), [11] as well as superior molecular sensitizer dyes [12] and the insertion of a barrier layer between the sensitizer dye and the HC. [2] To date, however, the desired redox intermediate mediators between the dye and I À /I 3 À redox electro-