Elsevier

Materials Letters

Volume 124, 1 June 2014, Pages 161-164
Materials Letters

TiO2 doped with different ratios of graphene and optimized application in CdS/CdSe quantum dot-sensitized solar cells

https://doi.org/10.1016/j.matlet.2014.03.062Get rights and content

Highlights

  • TiO2 was doped with different ratios of graphene and applied in quantum dot-sensitized solar cells (QDSSCs).

  • The efficiency of QDSSCs was changed with the ratios of graphene composition.

  • The QDSSCs incorporating 0.1 wt% graphene demonstrated a best power conversion efficiency of 2.8%.

Abstract

To optimize the performance efficiency of quantum dot-sensitized solar cells (QDSSCs), TiO2 doped with different ratios of graphene were prepared and applied in quantum dot-sensitized solar cells. The graphene–TiO2 nanocomposites were prepared by using hydrothermal synthesis of the alcohol–water system between graphene and TiO2 nanoparticles. It was found that the efficiency of quantum dot-sensitized solar cells was changed with the ratios of graphene composition. The CdS/CdSe quantum dot-sensitized solar cells incorporating 0.1 wt% graphene in the TiO2 photoanode demonstrated the most improvement in power conversion with an efficiency of 2.8%, which was 37% higher than that of pure TiO2.

Graphical abstract

TiO2 doped with different ratios of graphene were prepared and applied in quantum dot-sensitized solar cells. It was found that the efficiency of quantum dot-sensitized solar cells was changed with the ratios of graphene composition. The CdS/CdSe quantum dot-sensitized solar cells incorporating 0.1 wt% graphene in the TiO2 photoanode demonstrated the most improvement in power conversion with an efficiency of 2.8%, which was 37% higher than that of pure TiO2.

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Introduction

A need for clean and renewable energy resources has long motivated the interest in photovoltaic devices. A promising technology for converting sunlight into electrical energy is quantum dots-sensitized solar cells (QDSSCs) due to the ease and low cost of their generation [1], [2], [3], [4], [5]. However, the effective separation of photogenerated electrodes remains a major challenge in developing high-performance QDSSCs [6]. One strategy to accomplish separation has been the introduction of nanomaterials with suitable band energy as more efficient acceptors [7], [8]. One ideal building block in these nanocomposites is graphene [9]. Graphene is a two-dimensional material that has attracted much attention due to its unique properties, which include a large specific surface area [10], excellent thermal conductivity [11], high mobility of charge carriers [12], and optical transmittance [13]. Recently, development of graphene–inorganic nanocomposites has intensified and these nanocomposites have been found to exhibit a range of unique and useful properties. For these reasons, we report on in situ incorporation of increasing amounts of graphene in TiO2 nanoparticle films and its application in QDSSCs. We found that this incorporation of graphene significantly improved the photovoltaic performance.

Section snippets

Experimental details

Materials: All starting chemicals were analytical grade. TiO2 samples were synthesized by the Gratzel method [14] and graphene oxide (GO) was synthesized from graphite powder (99.99% Alfa Aesar) using a modification of the Hummers method [15]. Composites of TiO2 and graphene (GR) were synthesized by using the self-assembly method, whereby a 0.1 mg/ml GO aqueous solution was prepared by dissolving GO in distilled H2O by ultrasonic treatment. 1.5 ml of the 0.1 mg/ml GO aqueous solution and 0.3 g TiO2

Results and discussion

The H2O/methanol solvothermal condition reduces GO to graphene easily [17]. Fig. 1A shows the overall images of graphene/TiO2 composite. The enlarged view of the left blue marked area in Fig. 1A were displayed Fig. 1B, it can be seen that the TiO2 nanoparticle have uniform size and monodispersed. Fig. 1C was the enlarged view from the right blue marked eara in Fig. 1A, we can see clearly that TiO2 nanoparticles are well-dispersed and attached to the surface of graphene sheet. Fig. 1D shows XRD

Conclusion

In the work described here, we have demonstrated a simple and effective method to incorporate TiO2 nanoparticles with graphene sheets via hydrothermal synthesis of alcohol–water systems for application in QDSSCs. We found that the QDSSCs incorporating 0.1 wt% graphene in the TiO2 photoanode had the optimum conversion efficiency. We expect that the performance of the QDSSCs could be further improved by optimizing the graphene content and reduction process.

Acknowledgments

This research was supported by the Natural Science Foundation of China (Nos. U1162108 and 51272104); the Natural Science Foundation of Jiangsu Province Office of Education (Nos. 11KJA150002 and 10KJB150006), the Financial Foundation of State Key Laboratory of Materials-Oriented Chemical Engineering and a project funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions.

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