Dr.-Ing. Manuela Göbelt
Transparent conductive electrodes (TCEs) play an important role in all kind of optoelectronic devices, such as displays, solar cells or light emitting diodes (LEDs) . A new generation of TCEs should replace the widely used transparent conductive indium tin oxide (ITO), because of the scarcity of indium as well as the relatively high fabrication costs and the low flexibility of ITO thin films. Highly conductive metallic nanowire networks are one of the most promising alternatives to ITO, due to their excellent physical properties . However, the stability of silver nanowire (AgNW) networks in ambient conditions constitutes a significant disadvantage of this kind of electrode .
This project contributes to the development and characterization of a novel nano-composite electrode, which is based on encapsulated AgNW networks . The encapsulation in aluminum doped zinc oxide (ALD) is carried out by using atomic layer deposition (ALD), which guarantees a conformal and thickness controlled coating of the AgNWs (Figure 1b, c). Within the frame of this project, AgNW/AZO electrodes are fabricated and optimized concerning their optoelectronic properties and characterized by using a combination of SEM imaging and computer based analysis methods (Figure 1a) as well as TEM (STEM) techniques (Figure 1c). Furthermore, chemical and physical stability test are performed in order to determine the long-term stability of the nano-composite electrode. Investigations are also focused on the integration of the novel transparent electrode into different solar cell concepts.
Figure 1: a) Computer based analysis of a SEM image to determine the percolation of the AgNW network, b) SEM image of an encapsulated AgNW intersection, c) STEM cross-sectional image of an AgNW encapsulated by a 100 nm thick AZO layer  (Copyright 2015 Elsevier Ltd.).
 D. S. Ginley and J. D. Perkins, in: Handbook of Transparent Conductors, Boston, MA: Springer US, 2011, 1.
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 M. Göbelt et al., Nano Energy 16 (2015) 196.