Enhanced conversion efficiency of dye-sensitized solar cells using a CNT-incorporated TiO2 slurry-based photoanode

Jiaoping Cai,Jijun Zhang,Jun Li,Hai Li,Yan Wang,Dong Xiang,Zexiang Chen

doi:10.1063/1.4908179

Abstract

A new titanium dioxide (TiO2) slurry formulation is herein reported for the fabrication of TiO2 photoanode for use in dye-sensitized solar cells (DSSCs). The prepared TiO2 photoanode featured a highly uniform mesoporous structure with well-dispersed TiO2 nanoparticles. The energy conversion efficiency of the resulting TiO2 slurry-based DSSC was ∼63% higher than that achieved by a DSSC prepared using a commercial TiO2 slurry. Subsequently, the incorporation of acid-treated multi-walled carbon nanotubes (CNTs) into the TiO2 slurry was examined. More specifically, the effect of varying the concentration of the CNTs in this slurry on the performance of the resulting DSSCs was studied. The chemical state of the CNTs-incorporated TiO2 photoanode was investigated by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. A high energy conversion efficiency of 6.23% was obtained at an optimum CNT concentration of ∼0.06 wt.%. The obtained efficiency corresponds to a 63% enhancement when compared with that obtained from a DSSC based on a commercial TiO2 slurry. The higher efficiency was attributed to the improvement in the collection and transport of excited electrons in the presence of the CNTs.

Highlights

There has been considerable research interest in developing highly efficient dye-sensitized solar cells (DSSCs) since low-cost DSSCs based on titanium dioxide (TiO2) nanocrystalline electrodes displaying high energy conversion efficiencies were reported in 1991.1 The maximum energy conversion efficiency achieved by current state-of-the-art DSSCs is 12.3% at AM 1.5 G.2
The results confirmed that the anatase TiO2 nanocrystalline structure was retained following incorporation of carbon nanotubes (CNTs)–COOH and the treatments employed during the fabrication of the DSSC devices
The prepared TiO2 slurry was suitable for incorporating acid-treated CNTs that enabled efficient binding of the TiO2 nanoparticles, and aiding carbon polar groups to form one-dimensional fast-channel for excited electron transmission

Summary

Introduction

There has been considerable research interest in developing highly efficient dye-sensitized solar cells (DSSCs) since low-cost DSSCs based on titanium dioxide (TiO2) nanocrystalline electrodes displaying high energy conversion efficiencies were reported in 1991.1 The maximum energy conversion efficiency achieved by current state-of-the-art DSSCs is 12.3% at AM 1.5 G.2 progress in improving the performance of DSSCs further has been slow; the reported efficiency remains lower than the theoretical predicted values. Progress in improving the performance of DSSCs further has been slow; the reported efficiency remains lower than the theoretical predicted values. The effective methods to enhance the performance of DSSCs are mainly based on minimizing photo-generated electron–hole recombination in the TiO2 film and improving transport and transfer of photo-generated electrons.[3,4,5] These can be achieved by improving the morphology of the TiO2 film or employing composite films as electrodes. The porous structure and morphology of the TiO2 strongly influence the dye adsorption, diffusion of electrolytes, and sunlight harvesting.[6,7] Many experiments have been conducted to prepare TiO2 films with a good morphology and porous structure.[8,9,10,11,12,13] Maldonado-Valdivia et al studied the effect of varying the concentration of Triton X-100, polyethylene glycol 2000, or ethyl cellulose on the performance of DSSCs. The authors demonstrated that the film surface characteristics

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Conclusion