Proceedings of 6th International Conference on Hybrid and Organic Photovoltaics (HOPV14)
Publication date: 1st March 2014
Due to the recent rise in global warming from greenhouse gas bad effect on environment, the demand for renewable carbon-free energy sources is being given more and more attention. In this case solar energy is the unlimited source and promising candidate to substitute for old resources energy[1]. Dye-sensitized solar cells (DSCs) play the most crucial part of photovoltaic technologies because of their distinctive advantages against conventional silicon based materials, comprising low fabrication cost. Traditional liquid DSSCs based on liquid-based I/I3 redox couple to regenerate the dye have some drawback like potential leakage problems accompanying with the corrosive and volatile nature of the liquid electrolyte. Therefore, may be unfeasible for large-scale applications[2]. To address this problem for the first time Grätzel and coworkers in 1998 suggest solid-state dye sensitized solar cell (ssDSC) in which hole-transporting material (HTM) is one of the key components. However, the high cost of Spiro-OMeTAD due to the difficult synthesis of spirobifluorene core extremely limits its scale-up application. Seeking low-cost and high-efficiency HTMs is especially important.In between many HTM was synthesized like inorganic compound however development of this material is hindered due to limitation wide-band gap and main issue is their uncontrolled crystallization[3]. Many polymer HTM like Poly(3-hexylthiophen-2,5-diyl) (P3HT) and poly[2,6-(4,4-bis-(2-ethylhexyl)-4H-cyclopenta[2,1-b;3,4-b’]dithiophene)-alt-4,7-(2,1,3-benzothiadiazole)] (PCPDTBT) are used but one of the major problems when using a polymer as the HTM is the infiltration of the polymer into the nano-porousmetal oxide structure[4]. recently in Licheng Sun group reported some HTM based variety of triarylamine that can compete with Spiro-OMeTAD even though some of them has solubility problem[5]. To concur some of these problem we designed some new low-cost and easy-synthesisHTM based on Carbazol core with LEG4 dye as the photosensitizer. The oxidation potential value is very near to Spiro-OMeTAD potential (Figure 1 and Table1). Till now we got results with 4.5 % efficiency with good solubility that can compete with some of the former HTM. The experimental work with device is under progress.
Table 1 Oxidation potential of carbazol HTM
compound |
Spiro |
X18 |
X19 |
NHE |
0.63 |
0.581 |
0.606 |
Cyclic voltammetry in dichloromethane solution. 0.1Mtetrabutylammonium hexafluorophosphate has been added as a conduction salt. The applied potential was internally references vs the Fc+/Fc standard and then converts to Normal Hydrogen Electrode (NHE).
Figure 1. Molecular structures of X18, X19, Spiro-OMeTAD and LEG4
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