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3D hierarchical Zn2SnO4 microspheres show great potential as alternative photoanodes for dye-sensitized solar cells (DSSCs). Herein, hierarchical Zn2SnO4 microspheres with different sizes are fabricated via a one-step hydrothermal method, and a plausible formation process for Zn2SnO4 microspheres is proposed. The DSSCS devices based on 1.20 μm Zn2SnO4 microspheres show the best power conversion efficiency (PCE) of 4.00%. Further, TiCl4 treatment of a Zn2SnO4 microsphere photoanode results in an improved PCE up to 4.72%.

In this study, Zn2SnO4 nanoparticles with different sizes are successfully synthesized by a very convenient hydrothermal process. To sufficiently characterize the as-synthesized Zn2SnO4 nanoparticles, XRD, FE-SEM, TEM, UV and BET analyses are carried out. Moreover, the photocurrent response and photocatalytic activity properties of various Zn2SnO4 nanoparticles have been studied. The results indicate that the photocurrent response and photodegradation efficiency behavior of the 3.3 nm Zn2SnO4 nanoparticles are significantly superior to that of the 4.2 nm and 6.2 nm nanoparticles. It is due to small particle size effects with large surface-to-volume ratios, which can increase the number of active surface sites.

Engineered metal oxide anode materials highly affect the photovoltaic performance of solar cells. In this research, we fabricate double-layered ZnO nanoarray (NR)/ellipsoid or sphere films on a fluorine-doped tin oxide (FTO) substrate as photoanodes for dye-sensitized solar cells (DSSCs). The results indicate that DSSCs based on the double-layered ZnO NR/sphere film (∼3.19%) show an obvious 41.2% enhancement of power conversion efficiency (PCE) compared to the ZnO NR/ellipsoid film (∼2.26%), which is confirmed by IMPS, IMVS, EIS and UV-vis diffuse reflectance studies. This study provides a scheme for the selective combination of specific ZnO morphologies into an ideal photoanode configuration with more dye loading and superior light scattering ability for enhanced photovoltaic performance.

Hierarchical one-dimensional SnO2 nanofibers (NFs) consisting of nanoparticles (NPs) have been synthesized and employed as an efficient light scattering layer to fabricate double layered dye-sensitized solar cells (DSSCs). The photovoltaic performance (5.44%) of the DSSC based on the SnO2 NPs (14.5 μm)/NFs (4.0 μm) double layered photoanode showed a 26.3% enhancement compared to that of a SnO2 NPs photoanode (18.5μm, 4.30%). Intensity modulation photocurrent spectroscopy (IMPS), intensity-modulated voltage spectroscopy (IMVS) and open-circuit voltage decay (OCVD) spectroscopy were used to investigate the kinetic process of electron transport and recombination within SnO2 NPs or NPs/NFs based DSSCs, revealing a faster electron transport rate and a lower recombination rate in the SnO2 NPs/NFs photoanode. The UV-vis diffuse reflectance spectroscopy results showed that the SnO2 NPs/NFs possess better light scattering ability which enhanced their photovoltaic performance compared to the SnO2 NPs. Furthermore, an overall power conversion efficiency of 6.31% (with a Jsc of 16.78 mA cm−2, Voc of 711 mV and FF of 0.53) was achieved for the SnO2 NPs/NFs double layered photoanode with an additional SnO2 blocking layer, which suppressed electron recombination between the FTO glass and the electrolyte.