Viet Huong Nguyen1 2 Sara AghazadehChors1 3 César Masse de la Huerta1 Afzal Khan4 Carmen Jimenez1 Ngoc Duy Nguyen3 Delfina Muñoz2 Daniel Bellet1 David Munoz-Rojas1

1, Univ Grenoble Alpes, LMGP, CNRS, F38000, Grenoble, , France
2, CEA-INES, LITEN, F-73375, Le Bourget-du-Lac, , France
3, Département de Physique, Université de Liège, CESAM/Q-MAT, SPIN, Liège, , Belgium
4, Department of Physics, Univ. of Peshawar, Pakistan, Peshawar, , Pakistan

Transparent electrodes (TE) constitute a critical component within a wide range of devices including touch screens, solar cells, light emitting diodes (LEDs) or transparent heaters [1]. To date, the most commonly used transparent conductive material (TCM) is still indium tin oxide (ITO), however, the scarcity of indium and lack of flexibility of ITO have prompted the search for alternative materials. Among different types of emerging materials, the transparent electrodes based on silver nanowire (AgNW) networks exhibit excellent optical, electrical and mechanical properties fulfilling the requirements for many optoelectronic applications [2]. However, AgNW networks still suffer from thermal and electrical instabilities, requiring an effective and conformal protective layer. In addition, AgNW networks cannot act as an antireflective window or an effective collection layer in photovoltaic applications (because of free gaps between nanowires), which are usually ensured by a thin layer of metal oxide.
The aim of this contribution is to develop a composite electrode based on AgNW and metal oxide thin films such as zinc oxide (ZnO), aluminum oxide (Al2O3) or aluminum doped zinc oxide (AZO), which are printed by our home-made atmospheric pressure spatial atomic layer deposition system (AP-SALD) [3],[4]. We will show that a thin conformal ZnO coating deposited by APSALD technique can drastically enhance the stability of AgNW networks from 300°C up to 500°C. Similarly, while the electrical stability of uncoated AgNW network was 9V, ZnO coated network showed a 100% increase in electrical stability, up to 18V. The integration of the composite electrode to silicon heterojunction solar cell, as well as its implementation on flexible substrate, will be discussed.
In contrast to traditional fabrication processes, the APSALD technique relies on the possibility to print thin films in a vacuum-free, low-temperature (<200°C), low-cost and high throughput way (for instance compatible with roll-to-roll technology). Besides, the fabrication of AgNW networks involves also low-temperature processing steps and upscaling methods. Hence, the combination of both materials and their printable fabrication processes make this type of composite electrode very appropriate for future use, especially for flexible devices.
[1] K. Ellmer, “Past achievements and future challenges in the development of optically transparent electrodes,” Nat. Photonics, vol. 6, Nov. 2012.
[2] D. Langley et al., “Flexible transparent conductive materials based on silver nanowire networks: a review,” Nanotechnology, vol. 24, 2013.
[3] D. Muñoz-Rojas and J. MacManus-Driscoll, “Spatial atmospheric atomic layer deposition: a new laboratory and industrial tool for low-cost photovoltaics,” Mater. Horiz., vol. 1, 2014.
[4] V.H. Nguyen et al., “Deposition of ZnO based thin films by atmospheric pressure spatial atomic layer deposition for application in solar cells,” J. Renew. Sustain. Energy, vol. 9, Mar. 2017.