Abstract
Owing to its high electron mobility, zinc oxide represents a promising alternative to titanium dioxide as the working electrode material in dye-sensitized solar cells (DSCs). When zinc oxide is grown into 1-D nanowire arrays and incorporated into the working electrode of DSCs, enhanced electron dynamics and even a decoupling of electron transport (τ<sub>d</sub>) and electron lifetime (τ<sub>n</sub>) have been observed. In this work, DSCs with working electrodes composed of solution-grown, unarrayed ZnO nanorods are investigated. In order to determine whether such devices give rise to similar decoupling, intensity modulated photocurrent and photovoltage spectroscopies are used to measure τ<sub>d </sub>and τ<sub>n</sub>, while varying the illumination intensity. In addition, ZnO nanorod-based DSCs are compared with ZnO nanoparticle-based DSCs and nanomaterial shape is shown to affect electron dynamics. Nanorod-based DSCs exhibit shorter electron transport times, longer electron lifetimes, and a higher τ<sub>n</sub>/τ<sub>d</sub> ratio than nanoparticle-based DSCs.
Highlights
Since their introduction by O’Regan and Gratzel [1], dye-sensitized solar cells (DSCs) have continuously improved their performance
The working electrodes fabricated from each of the three nanomaterials are incorporated into DSCs and tested to determine the effect of particle shape and porosity on electron dynamics using intensity modulated photocurrent spectroscopy (IMPS) and intensity-modulated photovoltage spectroscopy (IMVS)
The results demonstrate that nanoparticle shape is a parameter that affects electron dynamics in ZnO DSC electrodes
Summary
Since their introduction by O’Regan and Gratzel [1], dye-sensitized solar cells (DSCs) have continuously improved their performance. The champion DSC boasts an efficiency exceeding 13% [2]. DSCs have inspired an entire class of perovskite-based devices that have demonstrated unprecedented leaps in power conversion efficiency given the short time they have been studied, improving to 15% efficiency in 2013 and to over 20% more recently [3,4,5,6]. DSCs are an attractive solar technology due to their low production cost, ease of manufacture, and potential for low light applications. Of the semiconductor materials that are used in DSCs, TiO2 and ZnO are reported most often [7,8].
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