The effects of pyridine derivative additives on interface processes at nanocrystalline TiO2 thin film in dye-sensitized solar cells

Key Laboratory of Photochemistry, Beijing National Laboratory for Molecular Sciences (BNLMS), Institute of Chemistry, Chinese Academy of Sciences

Graduate School of the Chinese Academy of Sciences

DOI: 10.1002/sia.2594

Abstract

2-Methyl-4-propoxypyridine, a new pyridine derivative, has been synthesized and used as an additive in the liquid electrolyte of dye-sensitized solar cells (DSSCs). Compared with 2-methylpyridne and 4-tertpyridine, they were employed to study the influence of the pyridine derivative additives on the rate of recombination at the electrode/dye/electrolyte interfaces and band edge shift of TiO2, which were measured by time-resolved mid-infrared absorption spectroscopy and Mott–Schottky analysis, respectively. It was found that the rate of interfacial charge recombination was enhanced when the pyridine derivative additives were present in the electrolyte. Meanwhile, the additives caused a negative shift of the band edge. However, the net effect of pyridine derivative addition was to improve the open-circuit photovoltage according to the photoelectrochemical measurement, indicating that negative shift of conduction band of TiO2 was a predominant factor in improving the open-circuit photovoltage. Also, the result was strongly supported by the dark current measurement. Therefore, it provides a microscopic account for the function of the pyridine derivative additives on the open-circuit photovoltage enhancement of the DSSCs. Furthermore, the decrease of the short-circuit photocurrent of the cells was also attributed to the slower dye regeneration due to the addition of additives from the results of cyclic voltammetry measurement.

Keywords

dye-sensitized solar cell; pyridine derivative additives; photovoltage enhancement; back electron transfer

Notes

This paper was written at the very beginning of the author's academic career, and its theme was also the main direction of the author's doctoral research - the design and synthesis of electrolyte additives for DSSCs. After four years of study and work, the author published this paper in Surf. Interface Anal. In the past nearly 20 years, this paper has received 50 citations, which is probably a great reward from the academic community for the author.