High-Efficiency, Solid-State, Dye-Sensitized Solar Cells Using Hierarchically Structured TiO2 Nanofibers

High-Efficiency, Solid-State, Dye-Sensitized Solar Cells Using Hierarchically Structured TiO2 Nanofibers
황대섭조성무김동영V. ArmelD.R. MacFarlene장성연
dye-sensitized solar cells; TiO2 nanofibers; solid-state electrolytes; plastic crystal; charge recommbination
Issue Date
ACS Applied Materials & Interfaces
VOL 3, NO 5, 1521-1527
High-performance, room-temperature (RT), solid-state dyesensitized solar cells (DSSCs) were fabricated using hierarchically structured TiO2 nanofiber (HS-NF) electrodes and plastic crystal (PC)-based solid-state electrolytes. The electrospun HS-NF photoelectrodes possessed a unique morphology in which submicrometer-scale core fibers are interconnected and the nanorods are dendrited onto the fibers. This nanorod-in-nanofiber morphology yielded porosity at both the mesopore and macropore level. The macropores, steming from the interfiber space, afforded high pore volumes to facilitate the infiltration of the PC electrolytes, whereas the mesoporous nanorod dendrites offered high surface area for enhanced dye loading. The solid-state DSSCs using HS-NFs (DSSC-NF) demonstrated improved power conversion efficiency (PCE) compared to conventional TiO2 nanoparticle (NP) based DSSCs (DSSC-NP). The improved performance (>2-fold) of the DSSC-NFs was due to the reduced internal series resistance (Rs) and the enhanced charge recombination lifetime (τr) determined by electrochemical impedance spectroscopy and intensity modulated photocurrent/ photovoltage spectroscopy. The easy penetration of the PC electrolytes into HS-NF layers via the macropores reduces Rs significantly, improving the fill factor (FF) of the resulting DSSC-NFs. The τr difference between the DSSC-NF and DSSC-NP in the PC electrolytes was extraordinary (~ 14 times) compared to reported results in conventional organic liquid electrolytes. The optimized PCE of DSSC-NF using the PC electrolytes was 6.54, 7.69, and 7.93%at the light intensity of 100, 50, and 30mWcm-2, respectively, with increased charge collection efficiency (>40%). This is the best performing RT solid-state DSSC using a PC electrolyte. Considering the fact that most reported quasi-solid state or nonvolatile electrolytes require higher iodine contents for efficient ion transport
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