Abstract
Cu- and Sm-doped ZnO nanorod arrays were grown with 1 wt% of Sm and different weight percents (0.0, 0.5, 1.0 and 1.5 wt%) of Cu by two-step hydrothermal method. The influence of Cu concentration and precursor of Sm on the structural, optical and photovoltaic properties of ZnO nanorod arrays was investigated. An X-ray diffraction study showed that the nanorod arrays grown along the (002) plane, i.e., c-axis, had hexagonal wurtzite crystal structure. The lattice strain is present in all samples and shows an increasing trend with Cu/Sm concentration. Field emission scanning electron microscopy was used to investigate the morphology and the nanorod arrays grown vertically on the FTO substrates. The diameter of nanorod arrays ranged from 68 nm to 137 nm and was found highly dependent on Cu concentration and Sm precursor while the density of nanorod arrays almost remains the same. The grown nanorod arrays served as photoelectrodes for fabricating dye-sensitized solar cells (DSSCs). The overall light to electricity conversion efficiency ranged from 1.74% (sample S1, doped with 1 wt% of Sm and 0.0 wt% of Cu) to more than 4.14% (sample S4, doped with 1 wt% of Sm and 1.5 wt% of Cu), which is 60% higher than former sample S1. The increment in DSSCs efficiency is attributed either because of the doping of Sm3+ ions which increase the absorption region of light spectrum by up/down conversion or the doping of Cu ions which decrease the recombination and backward transfer of photo-generated electrons and increase the electron transport mobility. This work indicates that the coupled use of Cu and Sm in ZnO nanorod array films have the potential to enhance the performance of dye-sensitized solar cells.
Highlights
Introduction conditions of the Creative CommonsOne-dimensional (1D) nanostructures have been an emerging class of oxide materials for the last few years because of their outstanding electrical and optoelectronic properties
The results show that the dye-sensitized solar cells (DSSCs) fabricated with 1 wt% of Sm and 1.5 wt% of Cu doped ZnO nanorod arrays exhibit better efficiency compared to that of DSSC fabricated with 1 wt% of
The very strong diffraction peak corresponding to (002) plane of ZnO at 2θ = 34.35◦ is observed in all samples
Summary
One-dimensional (1D) nanostructures have been an emerging class of oxide materials for the last few years because of their outstanding electrical and optoelectronic properties. These excellent properties of 1D nanostructures make them suitable for potential. Nanomaterials 2021, 11, 1710 applications in piezoelectric, gas sensing and solar cell devices [1,2,3,4]. There has been a huge interest in 1D ZnO nanostructures (nanowire/nanotube/nanorod arrays) as photoanodes in dye-sensitized solar cells because of low toxicity, reproducibility, facile and low temperature synthesis methods [5].
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