Effect of 4-tertbutyl pyridine and guanidinium thiocyanate Co-Additives on Performance of Dye-Sensitized Solar Cells Fabricated with Non-Volatile Liquid Electrolyte
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Date
2021
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Publisher
Uva Wellassa University of Sri Lanka
Abstract
Dye-sensitized solar cells (DSSCs) are emerging as potential candidates to substitute for expensive
silicon solar cells because of reasonably high efficiency, easy fabrication method, lower production
cost and transparency. Electrolyte modifications of DSSC are an easy way to enhance the
photovoltaic performance. The conventional liquid electrolyte system is composed of
iodide/triiodide single salt in the volatile, acetonitrile solvent. In this work, the non-volatile ethylene
carbonate (EC) and propylene carbonate (PC) were used with tetrapropyl ammonium iodide (Pr4NI)
salt to prepare the reference electrolyte. The effect of the co- additives 4-tert butylpyridine (TBP)
and Guanidinium thiocyanate (GuSCN) on the photovoltaic performance of DSSCs was also
studied. The addition of TBP as an additive into the iodide electrolyte system increased the
photovoltage (VOC) by 13.8%, but it reduced the photocurrent density (JSC) by 7.2%. However, the
JSC was increased by about 8.7% by the addition of GuSCN as the additive. The addition of the
combination of TBP and GuSCN binary additives in the optimized ratio of 65:35 enhanced the cell
efficiency from 5.63% to 6.83%. The overall efficiency enhancement has been explained by the
shifting of the conduction energy band edge of TiO2 due to the adsorption of species from the two
co-additives by TiO2 leading to the enhancement of both, the photocurrent density as well as the
photovoltage. TBP improves the VOC by a negative shift of the band-edge and also prevents the
electron recombination to I3- due to the blocking effect on the dye-absent active site of the TiO2
surface. The addition of GuSCN to TBP-added electrolyte restored the JSC by the positive shift of the
band-edge. The net effect is to increase the overall performance of DSSCs due to the synergistic
effect of the two co-additives.
Keywords: Photovoltaic effect; Co-additives; Band-edge shift; Non-volatile; VOC improver
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Keywords
Mineral Sciences, Materials Sciences, Sensitized Solar Cell, Electronic Engineering