1,1,2,2-tetrachloroethane (TeCA) as Solvent Additive for Organic Hole Transport Materials and Its Application in Highly Efficient Solid-state Dye-sensitized Solar Cells

International Conference on Hybrid and Organic Photovoltaics
Proceedings of International Conference on Hybrid and Organic Photovoltaics 2015 (HOPV15)

Poster, Bo Xu, 358
Publication date: 5th February 2015

A powerful method to improve the charge transport capacityand the overall electrical conductivity of organic semiconductors (OSs) is by using chemical doping ^[1]. This strategy has been used in p-type organic hole transport materials (HTMs), such as 2,2’,7,7’-tetrakis-(N,N-di-p-methoxyphenyl-amine)9,9’spiro-bifluorene (Spiro-OMeTAD) in solid-state dye-sensitized solar cells (ssDSCs)^[2-5]. To date, a section of effective chemical p-type dopants have been developed^[6-9]. However, some of the p-type dopants are strongly colored and compete with photosensitizer for the light absorption in the visible region; some of dopants exhibit poor solubility in organic solvents or high boiling points, making them unsuitable for fabrication of solution-processed photovoltaic devices. Most importantly, the majority of the p-type dopants are not easily obtained, their complicated synthesis and high-cost which may offer limitations for future large-scale production. So, it remains an immense space to develop low-cost, colorless and solution-processable p-type dopants for HTMs. Herein, we firstly report an inexpensive, chlorinated, organic solvent, 1,1,2,2-tetrachloroethane (TeCA), which can be both used as a co-solvent and an effective p-type dopant for the organic HTM-Spiro-OMeTAD in ssDSCs, and a record PCE of 7.7% was obtained for this family of ssDSCs in combination with the D-π-A-dye LEG4 as photosensitizer under standard solar irradiation (AM1.5G, 100 mW•cm^-2). The TeCA-doped devices exhibit much better device performance than that of the commonly used Cobalt(III)-FK209 and oxygen doping methods both in LEG4 and D102 dye-based ssDSCs. Furthermore, our results show that the TeCA doping method not only improves the device performance, but also exhibits better reproducibility than the known p-type dopants for ssDSCs. The successful application of TeCA provides new opportunities for the fabrication of low-cost and highly efficient ssDSCs. The method introduced also has a potential for applications in solution-processed organic field-effect transistors (OFETs) and organic light-emitting diodes (OLEDs) in the future.

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