Aqueous chemical synthesis of large-scale ZnO aggregates with high-efficient light-scattering and application in dye-sensitized solar cells

We report on the synthesis of polydisperse ZnO aggregates with large average diameter of 700 ± 150 nm comparable to the wavelengths of the visible region, and their implementation in both rigid and flexible photoanodes of dye-sensitized solar cells (DSCs). The ZnO aggregates were prepared through an aqueous chemical method in triethanolamine (TEA)-based aqueous system, followed by the characterizations of scanning electron microscopy (SEM), X-ray diffraction (XRD) and diffuse reflectance spectra (DRS). It was found that the size of as-prepared ZnO aggregates could be experimentally controlled by varying TEA concentrations initially added. With a TEA concentration of 25%, ∼700 nm-sized ZnO aggregates based film exhibited the highest reflectance of 75–90% in the visible wavelength region. The photoelectrical efficiencies of the corresponding cells based on rigid and flexible photoanodes were achieved maximum up to be 3.91% and 2.22% under 100 mW cm−2 AM 1.5 illumination, respectively. The excellent performance was mainly due to the more efficient light-harvest of the electrode film indicated by the incident photon-to-current efficiency (IPCE) and lower charge transfer resistance at the ZnO/dye/electrolyte interface evidenced by electrochemical impedance spectroscopy (EIS).

► An aqueous chemical method for preparing polydispersed ZnO aggregates is presented.
► TEA concentration is crucial to morphology and performance of ZnO electrode films.
► Efficiencies of 3.91% and 2.22% for rigid and flexible devices, respectively.
► Application of ZnO aggregates in the flexible photoanode for the first time.