Elsevier

Solar Energy

Volume 80, Issue 11, November 2006, Pages 1483-1488
Solar Energy

Quasi-solid state dye-sensitized solar cells based on gel polymer electrolyte with poly(acrylonitrile-co-styrene)/NaI+I2

https://doi.org/10.1016/j.solener.2005.11.007Get rights and content

Abstract

Gel polymer electrolyte based on poly(acrylonitrile-co-styrene)/NaI+I2 and binary solvent mixture was prepared. When the system contains 0.5 M NaI and 0.05 M I2, the maximum ionic conductivity (at 30 °C) of 2.37 mS cm−1 was achieved. Based on a gel polymer electrolyte with 0.5 M NaI, 0.05 M I2 and 0.5 M 4-tert-butylpyridine, a quasi-solid state dye-sensitized solar cell was fabricated and its overall energy conversion efficiency of light-to-electricity of 2.75% was achieved under irradiation of 60 mW cm−2.

Introduction

Dye-sensitized solar cells (DSSCs) have attracted great attention over the past decade as a low-cost alternative to traditional photovoltaic devices (O’ Regan and Grätzel, 1991, Nazeeruddin et al., 1993, Nazeeruddin et al., 2001). Light-to-electrical energy conversion efficiencies of DSSCs based on liquid electrolytes using organic compounds, such as acetonitrile, propylene carbonate and ethylene carbonate as solvents and iodide/triiodide (I-/I3) redox couple as an electrolyte have reached 10–11% under irradiation of AM 1.5 (Nazeeruddin et al., 1993, Nazeeruddin et al., 2001, Nakade et al., 2002, Gregg et al., 2003, Diamant et al., 2003). However, the leakage and evaporation of the liquid electrolyte caused by the technical difficulty in sealing has been a critical factor for long-term practical operation and causes substantial problems to put DSSCs into practical uses.

To overcome these problems, much effort has been made to replace the liquid electrolytes with solid or quasi-solid type charge transport materials (O’ Regan et al., 2002, Bach et al., 1998, Nogueira et al., 2001, Cao et al., 1995). Compared with other kinds of charge transport materials, the gel polymer electrolytes have some advantages including high ionic conductivities which are achieved by “trapping” a liquid electrolyte in polymer cages formed in a host matrix, good contacting and filling properties of the nanostructured electrode and counter electrode. Therefore, the gel polymer electrolytes have been attracting intensive attention. Up to the present, several types of gel electrolytes based on different kinds of polymers have already been used in quasi-solid state dye-sensitized solar cells (Cao et al., 1995, Wang et al., 2004, Matsumoto et al., 1996).

In this paper, poly(acrylonitrile-co-styrene) is used as a polymer matrix to trap liquid state electrolyte with NaI, I2 and binary organic solvent mixture to form gel polymer electrolyte. Poly(acrylonitrile-co-styrene) is an amorphous state which is good for solvent to immerge into polymer matrix to form gel state. The system has received relatively high ambient ionic conductivity. Quasi-solid state dye-sensitized solar cells were fabricated by sandwiching front and counter electrodes. Their photovoltaic performance was also evaluated.

Section snippets

Materials

Poly(acrylonitrile-co-styrene) was commercially obtained from a chemical company in China and used without further purification. Tetrabutyltitanate, titanium tetrachloride, sodium iodide, iodine, ethylene carbonate (EC), propylene carbonate (PC) and 4-tert-butylpyridine were all A.R. grade and purchased from Xilong Chemicals, China. All reagents were used without further treatment before using.

Conducting glass plates (FTO glass, Fluorine doped tin oxide over-layer, sheet resistance 8 Ω cm−2,

Influence of the concentration of NaI on the conductivity

It is well known that the inorganic iodide salt plays a key role in the ionic conductivity for the gel polymer electrolyte. In order to obtain the maximum value of the ambient ionic conductivity, the NaI concentration was varied in the gel polymer electrolyte and the result is shown in Fig. 1. The value of the ambient ionic conductivity originally increases and attains the maximum. The highest ionic conductivity about 2.37 mS cm−1 is attained at the NaI concentration of 0.5 M. Then the ionic

Conclusions

Gel polymer electrolyte based on poly(acrylonitrile-co-styrene)/NaI/I2 and binary solvent was prepared. The system was optimized and the maximum ionic conductivity (at 30 °C) of 2.37 mS cm−1 was achieved. It is found that the ionic conductivity of gel polymer electrolyte plays a crucial role on short-circuit current density. It can be concluded that 4-tert-butylpyridine has a great influence on photoelectrochemical performance. On adding 0.5 M TBP into gel polymer electrolyte, the overall energy

Acknowledgement

The authors gratefully acknowledge the financial support of the National Natural Science Foundation of China (No. 50572030, 50372022).

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