Thomas Neethu, Sharma Neha, Swaminathan Parasuraman
Electronic Materials and Thin Films Lab Dept. of Metallurgical and Materials Engineering, Indian Institute of Technology Madras, Chennai, 600036, India.
AMOLED research center, Dept. of Electrical Engineering, Indian Institute of Technology Madras, Chennai, 600036, India.
Nanotechnology. 2023 Nov 16;35(5). doi: 10.1088/1361-6528/ad07a1.
Transparent conducting films (TCFs) made by the assembly/deposition of silver nanowires (Ag NWs) are widely used to manufacture flexible electronics such as touch screens, heaters, displays, and organic light-emitting diodes. Controlling the dimensions (length and diameter) of the nanowires is key in obtaining TCFs with the desired optoelectronic properties, namely sheet resistance and optical transparency. This work describes a combined experimental and theoretical investigation on the optimization of the NW dimensions to fabricate high-quality TCFs. Ag NWs of different dimensions are synthesized by the modified polyol method and the average diameter and length of the wires are tailored over a wide range, 35-150 nm and 12-130m respectively, by controlling the synthesis parameters such as reaction conditions, stabilizing agents, and growth promoters. The synthesized NWs are spin coated on glass substrates to form TCFs. Comparing the films with different lengths, but identical diameters, enabled the quantification of the effect of length on the optoelectronic properties of the TCFs. Similarly, the effect of NW diameter is also studied. A non-uniformity factor is defined to evaluate the uniformity of the TCF and the transmittance of the NW network is shown to be inversely proportional to its area coverage. The sheet conductance versus the normalized number density is plotted for the different concentrations of NWs to extract a conductivity exponent that agrees well with the theoretical predictions. For thin film networks, the relation between the transmittance and sheet resistance provides the percolative figure of merit (FoM) as a fitting parameter. A large FoM is desirable for a good-performing TCF and the synthesis conditions to achieve this are optimized.
通过银纳米线（Ag NWs）的组装/沉积制成的透明导电薄膜（TCFs）被广泛用于制造柔性电子产品，如触摸屏、加热器、显示器和有机发光二极管。控制纳米线的尺寸（长度和直径）是获得具有所需光电性能（即薄层电阻和光学透明度）的TCFs的关键。这项工作描述了一项关于优化纳米线尺寸以制造高质量TCFs的实验与理论相结合的研究。通过改进的多元醇法合成了不同尺寸的Ag NWs，并通过控制反应条件、稳定剂和生长促进剂等合成参数，在很宽的范围内分别调整了纳米线的平均直径和长度，直径为35 - 150 nm，长度为12 - 130μm。将合成的纳米线旋涂在玻璃基板上以形成TCFs。比较不同长度但直径相同的薄膜，能够量化长度对TCFs光电性能的影响。同样，也研究了纳米线直径的影响。定义了一个不均匀因子来评估TCF的均匀性，并且表明纳米线网络的透过率与其面积覆盖率成反比。针对不同浓度的纳米线绘制薄层电导率与归一化数密度的关系图，以提取与理论预测吻合良好的电导率指数。对于薄膜网络，透过率与薄层电阻之间的关系提供了作为拟合参数的渗流品质因数（FoM）。对于性能良好的TCF，需要较大的FoM，并对实现这一目标的合成条件进行了优化。
