Photoelectrochemical solar cells made from SnO 2 /ZnO films sensitized with an indoline dye
- PDF / 503,836 Bytes
- 4 Pages / 584.957 x 782.986 pts Page_size
- 74 Downloads / 156 Views
Gamaralalege Rajanya Asoka Kumara Department of Chemistry, Peradeniya University, Peradeniya City 20400, Sri Lanka (Received 15 February 2010; accepted 18 May 2010)
A dye-sensitized photoelectrochemical (DS-PEC) cell consisting of SnO2 and ZnO nanoparticles was found to yield higher solar energy conversion efficiency than similar cells made of the individual oxide semiconductors when they were sensitized with an indoline dye. The SnO2/ZnO composite solar cell gave an overall energy conversion efficiency of 3.8% while the SnO2 and ZnO individual cells yielded efficiencies of 2.8% and 1.2%, respectively, under standard AM 1.5 irradiation (100 mW cm2). The broadening of the absorption spectra and a large red shift of the absorption peak were observed by the adsorbing dyes on the composite film suggesting the formation of various kinds of J-aggregates. It is suggested that the formation of the J-aggregates and the presence of the ZnO barrier were responsible for the higher efficiency of the composite cell. I. INTRODUCTION
Dye sensitization of wide band gap semiconductors has attracted much interest as a promising method for solar energy conversion.1–3 The dye-sensitized photoelectrochemical (DS-PEC) consists basically of a dyecoated semiconductor electrode and a counter electrode arranged in a sandwich configuration and the intervening space filled with an electrolyte containing a redox mediator (e.g., I3/I). The mechanism here is that upon illumination of an DS-PEC, an electron is injected from the excited state of the dye into the conduction band of the semiconductor followed by a hole transfer to the electrolyte. If the dye excited state lies energetically above the conduction band edge of the semiconductor, electron injection from the excited dye state to the semiconductor can occur on a fast or ultrafast time scale.4–7 The photoinjected electrons travel through the mesoporous network of the semiconductor nanostructure and are collected at the transparent conducting layer, where they move into the external circuit. Currently, dyed nanoporous TiO2 films of high surface area, efficiently transfer photoinjected carriers to the conducting substrates where the TiO2 film is deposited.8 Attempts have also been made to use nanoporous films of other semiconducting materials (e.g., ZnO, SnO2, Nb2O5) for the construction of dye-sensitized photoelectrochemical cells.9–11 However, DS-PEC constructed from these oxides yields a)
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/JMR.2010.0235
1838
http://journals.cambridge.org
J. Mater. Res., Vol. 25, No. 9, Sep 2010 Downloaded: 03 Apr 2015
low solar energy conversion efficiency (Z) compared to those based on TiO2. It has been demonstrated that a highly efficient DS-PEC made from a composite film consisting of SnO2 and ZnO can be made using the Ru-dye [ruthenium (II) cis-bis(thiocyanato)bis(2,2’bipyridil-4,4’-dicarboxylic acid) complex].12,13 Due to the presence of rare metals and the difficulty in purification of Ru-dyes, metal-fr
Data Loading...
