Abstract
Mesoporous SnO2 microspheres assembled from densely-packed nanocrystalline building units are a class of useful nanomaterials and have extensive optoelectronic applications, but so far it is still a challenge to acquire monodispersed microspheres. Here, monodispersed SnO2 microspheres consisted of aggregated small primary nanocrystallites are synthesized via a surfactant-free solvothermal method. These SnO2 microspheres have high specific surface area, excellent crystallinity and tunable building units. By precisely controlling the nucleation and growth, the obtained microspheres exhibit narrow size distribution, whose diameters are 200 ± 17 and 191 ± 16 nm from pure n-propanol and n-propanol/water mixed solvents, respectively. The sizes of primary nanocrystals slightly increase with the adscititious water. The SnO2 microspheres exhibit large specific surface areas, leading to efficient sensitizer-loading in both dye-sensitized solar cells (DSSCs) and perovskite solar cells (PSCs). The sub-micron-sized microspheres could also enhance the light-harvesting of the solar cells due to their light-scattering capability. As the primary nanocrystal multiply contacts densely to neighbouring grains, such intergrowth would improve the electron transport through the grain boundaries. Eventually, a power conversion efficiency of 3.83% is yielded for pure SnO2-based DSSCs when the SnO2 microspheres are used as the scattering layers, and an efficiency of 15.41% is obtained when they are used as the electron transport layers in PSCs.
Published Version
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