Abstract
Dye sensitized solar cells (DSSCs), described as one of the most prominent third generation solar cells, stand out in the photovoltaic category. In general, DSSCs consist of a large band gap n-type semiconductor electrode (photoanode), a sensitizer (dye), a redox electrolyte, and a counter electrode (CE). A platinized glass substrate is commonly used as the CE which acts as a catalyst for the redox reaction taking place in the cell. Further, it collects electrons from the external load and sends them to the electrolyte. Although Pt has several advantages characteristics, Pt free CE materials have drawn the attention of researchers because Pt is an extremely expensive and diminishing noble metal. According to various researches, carbonaceous materials are promising alternatives for the Pt CE. In this study we report the use of Sri Lankan vein graphite/polyaniline (SLVG/PANI) composite as the counter electrode material for DSSCs. Sri Lankan vein graphite (SLVG) is highly crystalline and is a potential low cost alternative to expensive Pt. Polyaniline was prepared by oxidative polymerization of aniline with potassium peroxydisulfate. SLVG/PANI composites were screen printed on fluorine doped tin oxide (FTO) glass substrate using carboxymethyl cellulose (CMC) as the binder. The performance of the new counter electrode was studied by analyzing the I-V characteristics of the DSSCs and the highest efficiency of 5.0% was recorded. DSSCs with new counter electrodes were further characterized using powder X-ray diffraction and Fourier Transform Infrared studies.
Highlights
The energy demand with the development of the quality of human life is projected to be increased by 48% from 2012 - 2040 for a period of 28 years (Cases, 2019)
poly(ethylene glycol) (PEG) did not show promising characteristics as a binder since the counter electrode materials including PANI, Sri Lankan vein graphite (SLVG) and PANI/SLVG composites were tend to peel off with PEG upon introducing the liquid electrolyte. This could have been overcome by employing high temperature, sintering was not done during the fabrication, since there is a possibility of polymer degradation at high temperatures
In addition to the strong binding capability, due to aligning of the PANI molecules, it is stated that carboxymethyl cellulose (CMC) leads to a more ordered chain which results in better conductivity, since these arrangement of molecules flatten the structure of molecule in the region of delocalization occurs
Summary
The energy demand with the development of the quality of human life is projected to be increased by 48% from 2012 - 2040 for a period of 28 years (Cases, 2019). This study reports the use of SLVG/PANI composite as the CE material for DSSCs. Sri Lankan vein graphite is highly crystalline and is a good low-cost material with a good electrical conductivity. The SLVG/PANI composite reported in this study would be a promising alternative counter electrode material for DSSCs with enhanced conductivity, reduced cost and easy fabrication process compared to the conventional Pt counter electrode. Many methods such as screen printing, doctor blade, thermal decomposition, electrochemical deposition etc. Desired thickness of the active film can be obtained by repeating the printing process several times
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