Polymer Hybrids Center, Korea Institute of Science and Technology, Seoul, Korea.
ACS Appl Mater Interfaces. 2011 May;3(5):1521-7. doi: 10.1021/am200092j. Epub 2011 Apr 15.
High-performance, room-temperature (RT), solid-state dye-sensitized 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 (R(s)) and the enhanced charge recombination lifetime (τ(r)) 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 R(s) significantly, improving the fill factor (FF) of the resulting DSSC-NFs. The τ(r) 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 30 mW cm⁻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, our HS-NFs are a promising morphology for such electrolytes that have limited ion mass transport.
采用分层结构 TiO₂ 纳米纤维（HS-NF）电极和基于塑料晶体（PC）的固态电解质，制备了高性能、室温（RT）、固态染料敏化太阳能电池（DSSC）。电纺 HS-NF 光电电极具有独特的形态，其中亚微米级别的芯纤维相互连接，纳米棒在纤维上呈树枝状。这种纳米棒在纳米纤维中的形态在介孔和大孔水平上产生了孔隙率。大孔源自纤维间的空间，提供了高孔体积，有利于 PC 电解质的渗透，而介孔纳米棒枝晶提供了高的比表面积，有利于增强染料负载。与传统的基于 TiO₂ 纳米颗粒（NP）的 DSSC（DSSC-NP）相比，使用 HS-NFs（DSSC-NF）的固态 DSSC 显示出了更高的功率转换效率（PCE）。DSSC-NF 的性能提高（提高了 2 倍以上）归因于电化学阻抗谱和强度调制光电流/光电压谱确定的内部串联电阻（R(s)）降低和电荷复合寿命（τ(r)）增强。PC 电解质通过大孔很容易渗透到 HS-NF 层中，显著降低了 R(s)，从而提高了所得 DSSC-NF 的填充因子（FF）。与在传统有机液体电解质中报道的结果相比，DSSC-NF 和 DSSC-NP 在 PC 电解质中的 τ(r) 差异非常大（约 14 倍）。在 100、50 和 30 mW cm⁻² 的光强下，使用 PC 电解质的 DSSC-NF 的优化 PCE 分别为 6.54%、7.69%和 7.93%，电荷收集效率提高了（>40%）。这是使用 PC 电解质的性能最佳的 RT 固态 DSSC。考虑到大多数报道的准固态或不可挥发电解质需要更高的碘含量来实现有效的离子传输，我们的 HS-NF 是一种很有前途的形态，适用于离子质量传输有限的电解质。
