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以氧化铟锡(indium tin oxide, ITO)为代表的透明导电氧化物(transparent conducting oxide, TCO)在当前光电器件中的重要性日益增长. 通过在TCO中引入金属网格构成复合电极, 可以在保持良好透明性的前提下有效提升电学性能, 同时降低对铟的需求量, 并为可穿戴设备所需的柔性电极提供可能方案. 对此类电极的电学性能分析, 如复合电极方阻随金属网格结构参数的变化, 可为电极设计与制备提供基本的出发点, 但相关理论尚十分缺乏. 本文针对典型的方孔方格型金属网格-TCO复合电极, 分别展开基于瑞利模型和基于有限元仿真的电学性能分析. 结果表明, 孔型近似导致的金属通道显著畸变是复合电极的电学计算中瑞利模型在中高开口率下失效的主要原因. 据此, 我们采用格型修正, 通过提升瑞利模型中的原胞外边界对称性来改善金属通道的畸变. 与电极仿真的对比表明, 修正后瑞利模型的适用范围明显扩大, 其结果可与实验数据很好地拟合, 为此类复合透明电极的电学数据分析与结构设计提供了简洁高效的理论工具.Transparent conducting oxides (TCOs), especially indium tin oxides (ITOs), have played an important role in realizing optoelectronics devices. Composite electrodes fabricated by introducing different types of metal-meshes into TCO have exhibited improved electric properties as well as good transparency. This technology can also reduce the demand for ITO and provide the candidates of flexible electrodes for wearable devices. Analysis of the electric properties of this type of electrode, such as the variance of the sheet resistance of the composite electrodes with the embedded mesh structure parameters, can provide a theoretical basis for designing and fabricating this electrode. But detailed studies are still lacking. This work focuses on the electrical property analysis of the typical square hole and grid shaped metal mesh-TCO composite electrodes based on Rayleigh model and finite-element simulation, respectively. The electric potential distribution and current density distribution are obtained from the finite element calculations, revealing that the dramatic deformation of the metallic channels in the composite results in the failure of a conventional Rayleigh model for the moderate and high opening rates. Accordingly, we adopt a lattice correction to the Rayleigh model to reduce the channel deformation by increasing the symmetry of the exterior boundary of the lattice cell. A comparison of the results from the simulations with those from the second-order approximation of the lattice-adapted Rayleigh model shows that the new analytic form of the effective conductivity is applicable to a much larger opening-rate range for both the monolayer and the sandwich structures of metal-mesh TCO composite electrodes. The variances of the sheet resistance and the effective conductivity with different material and structure parameters of the composite electrodes are calculated and discussed based on the lattice-adapted Rayleigh approximation. The results are well consistent with experimental results. A comparison of our model with other theoretical models is also made, showing that this lattice-adapted Rayleigh approximation can be used as a simple and efficient theoretical tool to analyze and design the concerned transparent composite electrodes.
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Keywords:
- transparent conductors/
- metal mesh electrodes/
- composites medium/
- finite element simulation
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$h$/${\text{nm}}$ 8 10 12 14 16 18 20 ${\rho _{{\text{Ag}}}}$/(${\text{μ}}\,\Omega{\cdot} {\text{cm}}$) $37.8$ $18.6$ $7.94$ $7.10$ $6.51$ $4.91$ $4.64$ ${p_{\text{c}}}$ — 0 0.4675 0.5525 0.6375 0.7225 0.7650 
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