Composite semiconductor quantum dots CdSe/CdS Co-sensitized TiO₂ nanorod array solar cells

Abstract

CdSe/CdS semiconductor quantum dots co-sensitized TiO₂ nanorod array was fabricated on the transparent conductive fluorine-doped tin oxide (FTO) substrate using the hydrothermal and successive ionic layer adsorption and reaction (SILAR) process. The structural and morphological properties of the samples were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM). The results indicate that CdSe/CdS QDs are uniformly coated on the surface of the TiO₂ nanorods. The shift of light absorption edge was monitored by taking UV-visible absorption spectra. Compared with the absorption spectra of the TiO₂ nanorod array, deposition of CdSe/CdS QDs shifts the absorption edge to the higher wavelength. The enhanced light absorption in the visible-light region of CdSe/CdS/TiO₂ nanorod array indicates that CdSe/CdS layers can act as co-sensitizers in quantum dots sensitized solar cells (QDSSCs). By optimizing the CdSe layer deposition cycles, a photocurrent of 5.78 mA/cm², an open circuit photovoltage of 0.469 V and a conversion efficiency of 1.34 % were obtained under an illumination of 100 mw/cm².

Keywords

quantum dots / TiO₂ nanorod array / solar cells / photovoltaic performance

References

[1] O’Regan B., Grätzel M. A Low-cost, High-efficiency Solar Cell Based on Dye-sensitized Colloidal TiO₂ Films [J]. Nature, 1991, 353(6346): 737-740.

[2] Peter L. M., Riley D. j., Tull E. J., . Photosensitization of Nanocrystalline TiO₂ by Self-assembled Layers of CdS Quantum Dots[J]. Chem. Commun., 2002, 10: 1 030-1 031.

[3] Robel I., Subramanian V., Kuno M., . Quantum Dot Solar Cells. Harvesting Light Energy with CdSe Nanocrystals Molecularly Linked to Mesoscopic TiO2 Films[J]. J. Am. Chem. Soc., 2006, 128(7): 2 385-2 393.

[4] Plass R., Serge P., Krüger J., . Quantum Dot Sensitization of Organic-Inorganic Hybrid Solar Cells [J]. J. Phys. Chem. B, 2002, 106(31): 7 578-7 580.

[5] Blackburn J. L., Selmarten D. C., Ellingson R. J., . Electron and Hole Transfer from Indium Phosphide Quantum Dots [J]. J. Phys. Chem. B, 2005, 109(7): 2 625-2 631.

[6] Kongkanand A., Tvrdy K., Takechi K., . Quantum Dot Solar Cells. Tuning Photoresponse through Size and Shape Control of CdSe-TiO2 Architecture [J]. J. Am. Chem. Soc., 2008, 130(12): 4 007-4 015.

[7] Nozik A. J. Excition Multiplication and Relaxation Dynamics in Quantum Dots: Applications to Ultrahigh-Efficiency Solar Photon Conversion [J]. Inorg. Chem., 2005, 44(20): 6 893-6 899.

[8] Hanna M. C., Nozic A. J. Solar Conversion Efficiency of Photovoltaic and Photoelectrolysis Cells with Carrier Multiplication Absorbers[J]. J. Appl. Phys., 2006, 100(7): 074 510

[9] Tian Z. R., Voigt J. A., Liu J., . Large Oriented Arrays and Continuous Films of TiO₂-Based Nanotubes[J]. J. Am. Chem. Soc., 2003, 125(41): 12 384-12 385.

[10] Liu B., Aydil E. S. Growth of Oriented Single-Crystalline Rutile TiO₂ Nanorods on Transparent Conducting Substrates for Dye-Sensitized Solar Cells [J]. J. Am. Chem. Soc., 2009, 131(11): 3 985-3 990.

[11] Feng X. J., Shankar K., Varghese O. K., . Vertically Aligned Single Crystal TiO₂ Nanowire Arrays Grown Directly on Transparent Conducting Oxide Coated Glass: Synthesis Details and Applications [J]. Nano Lett., 2008, 8(11): 3 781-3 786.

[12] Sun W. T., Yu Y., Pan H. Y., . CdS Quantum Dots Sensitized TiO₂ Nanotube-Array Photoelectrodes[J]. J. Am. Chem. Soc., 2008, 130(4): 1 124-1 125.

[13] Lee W. J., Kang S. H., Min S. K., . Co-sensitization of Vertically Aligned TiO₂ Nanotubes with Two Different Sizes of CdSe Quantum Dots for Broad Spectrum[J]. Electrochem. Commun., 2008, 10(10): 1 579-1 582.

[14] Chen H., Fu W. Y., Yang H. B., . Photosensitization of TiO₂ Nanorods with CdS Quantum Dots for Photovoltaic Devices[J]. Electrochimica Acta, 2010, 56(2): 919-924.

[15] Grätzel M. Photoelectrochemical Cells[J]. Nature, 2001, 414(6861): 338-344.

[16] Wang H., Bai Y. S., Zhang H., . CdS Quantum Dots-Sensitized TiO₂ Nanorod Array on Transparent Conductive Glass Photoelectrodes[J]. J. Phys. Chem. C, 2010, 114(39): 16 451-16 455.

[17] Lee H. J., Wang M. K., Chen P., . Efficient CdSe Quantum Dot-Sensitized Solar Cells Prepared by an Improved Successive Ionic Layer Adsorption and Reaction Process[J]. Nano Lett., 2009, 9(12): 4 421-4 424.

[18] Lee Y. L., Lo Y. S. Highly Efficient Quantum-Dot-Sensitized Solar Cell Based on Co-Sensitization of CdS/CdSe[J]. Adv. Func. Mater., 2009, 19(4): 604-609.

[19] Seol M. S., Kim H. J., Tak Y. J., . Novel Nanowire Array Based Highly Efficient Quantum Dot Sensitized Solar Cell [J]. Chem. Commun., 2010, 46(30): 5 521-5 523.