The effect of photoanode thickness on the performance of dye-sensitized solar cells containing TiO 2 nanosheets with exp
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Nanosized anatase TiO2 nanosheets with highly exposed reactive {001} facets (;80%) were prepared via hydrothermal reaction with the addition of hydrofluoric acid and characterized by various techniques including transmission electron microscopy, x-ray diffraction, x-ray photoelectron spectroscopy, and Brunauer–Emmett–Teller. High-quality TiO2 nanosheets films with different thicknesses (;5–20 lm) were fabricated by doctor blading, and the effect of film thickness on the performance of dye-sensitized solar cells (DSSCs) was investigated by I-V characterization and dark current potential scan. The results show that each parameter of DSSCs performance depends strongly on the thickness of the TiO2 nanosheets films. An optimized DSSCs performance of 8.39% was obtained by the TiO2 nanosheets film with a thickness of ;15 lm. I. INTRODUCTION
Since the significant progress has been achieved on low-cost dye-sensitized solar cells (DSSCs) by Professor Grätzel in 1991,1 the DSSCs have attracted extensive attention and been regarded as a promising candidate for the next-generation solar cells. The overall solar to current conversion efficiency over 11% has been reached under standard AM1.5 solar illumination2 exceeding that of the amorphous silicon solar cells. The most extensively explored type of DSSCs are composed of four main components: (i) a sensitizer attached to (ii) a porous semiconductor film on conducting glass substrate, which forms the photoanode, (iii) a Pt-sputtered conducting glass known as counter electrode, and (iv) an electrolyte solution in between. Basically, TiO2 is the most commonly used semiconductors in DSSCs due to its advantages in terms of its low cost, nontoxicity, and high chemical stability.3 Among all kinds of morphology, nanosized TiO2 materials have attracted widespread attention as it provides a high specific surface area for dye absorption, thus efficiently increasing the light harvesting yield compared with the same bulk material. Recently, extensive interest has been drawn in the synthesis of anatase TiO2 nanosheets with exposed {001} facets as the {001} surface of anatase TiO2 is much more reactive than the thermodynamically more stable {101} counterpart indicated by both theoretical and experimental studies, which would be favorable for photovoltaic cells, photodegradation of organic molecules, and photocatalytic
II. EXPERIMENTAL
a)
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2012.372
Anatase TiO2 nanosheets with exposed {001} facets were prepared by a hydrothermal method.8 Typically,
J. Mater. Res., Vol. 28, No. 3, Feb 14, 2013
http://journals.cambridge.org
water splitting applications.4,5 We recently reported the preparation of microsized anatase single crystals with 47% of exposed highly reactive {001} facets in 2008.6 In a more recent paper, we demonstrated the correlation between the particle morphology and the photoconversion efficiency of the nanosized anatase TiO2 single crystals with different percentages of exposed {001} facets.7 Experimenta
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