CdS quantum dot-sensitized solar cells based on nano-branched TiO 2 arrays
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NANO EXPRESS
Open Access
CdS quantum dot-sensitized solar cells based on nano-branched TiO2 arrays Chang Liu1, Yitan Li1, Lin Wei2, Cuncun Wu1, Yanxue Chen1*, Liangmo Mei1 and Jun Jiao3
Abstract Nano-branched rutile TiO2 nanorod arrays were grown on F:SnO2 conductive glass (FTO) by a facile, two-step wet chemical synthesis process at low temperature. The length of the nanobranches was tailored by controlling the growth time, after which CdS quantum dots were deposited on the nano-branched TiO2 arrays using the successive ionic layer adsorption and reaction method to make a photoanode for quantum dot-sensitized solar cells (QDSCs). The photovoltaic properties of the CdS-sensitized nano-branched TiO2 solar cells were studied systematically. A short-circuit current intensity of approximately 7 mA/cm2 and a light-to-electricity conversion efficiency of 0.95% were recorded for cells based on optimized nano-branched TiO2 arrays, indicating an increase of 138% compared to those based on unbranched TiO2 nanorod arrays. The improved performance is attributed to a markedly enlarged surface area provided by the nanobranches and better electron conductivity in the one-dimensional, well-aligned TiO2 nanorod trunks. Keywords: TiO2; CdS; Nanobranch; Solar cells
Background Solar cells have attracted considerable attention because of their potential application in low-cost and flexible energy generation devices. Since the seminal work pioneered by O'Regan and Grätzel in 1991, dye-sensitized solar cells have been investigated extensively all over the world [1-11]. Assembly of branched nanostructures also received intense scrutiny due to their potential effects to a number of promising applications such as solar cells, water splitting, optoelectronics, sensing, field emission, and more [12,13]. In 2013, Roh et al. studied solar cells based on nano-branched TiO2 nanotubes, specifically, nanotubes characterized by increased surface area [14]. The results were attractive; they were able to achieve an impressive light-to-electricity conversion rate. Also of note, Roh et al. used organic dye as a sensitizer to fabricate solar devices. However, the use of dye as a sensitizer is problematic for two reasons: first, organic dye is expensive; second, and perhaps more importantly, the organic dye proved to be unstable. As a result, using dye
* Correspondence: [email protected] 1 School of Physics and State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100, People's Republic of China Full list of author information is available at the end of the article
to sensitize solar cells is still not feasible for practical applications. Because it is critical to tailor materials to be not only cost-effective but also long-lasting, inorganic semiconductors such as CdSe [15,16], PbS [17-19], CdS [20], and Sb2S3 [21,22] have several advantages over conventional dyes: first, the band gap of semiconductor nanoparticles can be tuned by size to match the solar spectrum; second, their large intrinsic dipole moments can lead to rapid charge
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