Omnidirectional light harvesting enhancement of dye-sensitized solar cells decorated with two-dimensional ZnO nanoflowers

In this study, the chemical solution method was used to separately fabricate one-dimensional (1D) zinc oxide (ZnO) nanorods (NRs) and two-dimensional (2D) ZnO nanoflowers (NFs) on photoelectrodes for use in dye-sensitized solar cells (DSSCs). ZnO nanostructures (NSs) with different dimensions were grown on the photoelectrodes, and the effects of the NSs on the omnidirectional light-harvesting characteristics of the DSSCs and their bandgap were evaluated. The crystal structures and morphologies of the ZnO NSs were analysed using X-ray diffraction analysis and field-emission scanning electron microscopy, while their dye-adsorption characteristics were determined using an ultraviolet–visible–near infrared spectrometer. In addition, the finite-difference time-domain method was used to simulate the effects of the dimensions of the NSs on their light-scattering properties. The photoelectrodes with the ZnO NSs with different dimensions were then used to construct DSSCs, which were tested using electrochemical impedance spectroscopy as well as with a monochromatic incident photon-to-electron conversion efficiency measurement system and a solar simulator. Furthermore, with an increase in the incidence angle, the light-conversion efficiency of the 1D ZnO NRs reduced by 63.6% while that of the 2D ZnO NFs reduced only by 12%. Thus, DSSCs based on the 2D ZnO NFs are capable of capturing multidirectional incident light and hence ideal for use under scattered-light conditions. © 2019 Elsevier B.V.