Engineered Interfacial and Configuration Design of Double Layered SnO2@TiO2-ZnO Nanoplates Ternary Heterostructures for Efficient Dye-Sensitized Solar Cells

• The 2D hierarchical ZnO nanoplates can be successfully fabricated via a facile sonochemical process.
• The band-structure-matched hybrid ZnO-TiO2-SnO2 photoanodes were designed.
• An overall power conversion efficiency of ∼6.37% was achieved for the SnO2@TiO2-ZnO nanoplates hybrid photoanodes with SnO2 blocking layer.

The engineered interfacial and configuration design of anode materials plays pivotal role in photovoltaic performance of solar cells. Here we demonstrated a double layered SnO2@TiO2-ZnO nanoplates composite films on fluorine-doped tin oxide (FTO) substrate as photoanodes for high-performance dye-sensitized solar-cells (DSSCs). The results indicate that DSSCs based on double layered SnO2@TiO2-ZnO nanoplates composite film (∼5.55%) show an obvious 29.1% increase of power conversion efficiency as compared to the single layered SnO2@TiO2 nanoparticles photoelectrode with the same thickness of ∼18.5 μm. Intensity-modulated photocurrent/photovoltage spectroscopy (IMPS/IMVS) as well as electrochemical impedance spectra (EIS) measurements show that the double layered SnO2@TiO2-ZnO nanoplates film has faster electron transport rate and slower electron recombination rate than the SnO2@TiO2 one. Furthermore, final power conversion efficiency has been optimized to reach up ∼6.37% (Jsc of 17.18 mA cm−2, Voc of 742 mV and FF of 0.50) for the double layered SnO2@TiO2-ZnO nanoplates film photoanodes with the introduction of additional SnO2 blocking layer which would suppress the electron recombination between FTO glass and electrolyte. One of the specific advantages of the unique structure is the engineered integration of different promising materials, which made it possible to take full advantages of the superior dye adsorption, charge collection, charge transfer dynamics as well as optical scattering simultaneously. This study provides a scheme to selective combination of specific semiconductors metal oxides, namely, SnO2, TiO2 and ZnO, into an ideal photoanode configuration according to the feasible electron injection and transport dynamics, which has been regarded as promising photoanode materials for DSSCs. Fundamentally, this unique structure not only enables the high-efficiency solar cells application, but also provides a scheme for the inspiration of materials integration and guidance of effective materials surface and interfacial modification.

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