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Nano Research

Article Title

Inside-out Ostwald ripening: A facile process towards synthesizing anatase TiO2 microspheres for high-efficiency dye-sensitized solar cells

Keywords

Ostwald ripening, dye-sensitized solar cell, TiO2 microsphere, hollow structure, acetylacetone

Abstract

A facile inside-out Ostwald ripening route to the morphology-controlledpreparation of TiO2 microspheres is developed. Here, TiO2 hollow microspheres(HM) and solid microspheres (SM) are prepared by adjusting the volume ratio ofisopropanol (IPA) to acetylacetone (Acac) in the solvothermal process. Duringthe formation process of HM, precipitation of solid cores, subsequent depositionof outer shells on the surface of cores, and simultaneous core dissolution andshell recrystallization are observed, which validate the inside-out Ostwald ripeningmechanism. Design and optimization of the properties (pore size, surface area,and trap state) of TiO2 microspheres are vital to the high performance of dyesensitizedsolar cells (DSSCs). The optimized TiO2 microspheres (rHM and rSM)obtained by post-processing on recrystallization, possess large pore sizes, highsurface areas and reduced trap states (Ti3+ and oxygen vacancy), and are thusideal materials for photovoltaic devices. The power conversion efficiency of DSSCsfabricated using rHM photoanode is 11.22%, which is significantly improvedcompared with the 10.54% efficiency of the rSM-based DSSC. Our work providesa strategy for synthesizing TiO2 microspheres that simultaneously accommodatedifferent physical properties, in terms of surface area, crystallinity, morphology,and mesoporosity.

Graphical Abstract

Publisher

Tsinghua University Press

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