Materials properties are the keystone of functional devices for energy including energy conversion, harvesting or storage. But to market new energy materials, the development of suitable processing methods allowing affordable prices is needed. Recently, a new approach to atomic layer deposition (ALD) has gained much momentum. This alternative approach is based on separating the precursors in space rather than in time, and has therefore been called Spatial ALD (SALD). With SALD, the purge steps typical of ALD are not needed and thus deposition rates a hundred times faster are achievable. Additionally, SALD can be easily performed at ambient atmosphere, thus it is easier and cheaper to scale up than conventional ALD. This opens the door to widespread industrial application of ALD for the deposition of energy materials for applications including solar energy, energy storage, or smart windows. SALD is presented here and examples of application to photovoltaics and transparent conductive materials are given. We show that SALD is capable of producing high-quality films fully suited for device integration.

The past few years have seen a considerable amount of research devoted to nanostructured transparent conducting materials (TCM), which play a pivotal role in many modern devices such as solar cells, flexible light-emitting devices, touch screens, electromagnetic devices, and flexible transparent thin film heaters. Currently, the most commonly used TCM for such applications (ITO: Indium Tin oxide) suffers from two major drawbacks: brittleness and indium scarcity. Among emerging transparent electrodes, silver nanowire (AgNW) networks appear to be a promising substitute to ITO since such electrically percolating networks exhibit excellent properties with sheet resistance lower than 10 Ω/sq and optical transparency of 90%, fulfilling the requirements of most applications. In addition, AgNW networks also exhibit very good mechanical flexibility. The fabrication of these electrodes involves low-temperature processing steps and scalable methods, thus making them appropriate for future use as low-cost transparent electrodes in flexible electronic devices. This contribution aims to briefly present the main properties of AgNW based transparent electrodes as well as some considerations relating to their efficient integration in devices. The influence of network density, nanowire sizes, and post treatments on the properties of AgNW networks will also be evaluated. In addition to a general overview of AgNW networks, we focus on two important aspects: (i) network instabilities as well as an efficient Atomic Layer Deposition (ALD) coating which clearly enhances AgNW network stability and (ii) modelling to better understand the physical properties of these networks.

Whereas the integration of silver nanowires in functional devices has reached a fair level of maturity, the integration of copper nanowires still remains difficult, mainly due to the intrinsic instability of copper nanowires in ambient conditions. In this paper, copper nanowire based transparent electrodes with good performances (33 Ω sq ⁻¹ associated with 88% transparency) were obtained, and their degradation in different conditions was monitored, in particular by electrical measurements, transmission electron microscopy, x-ray photoelectron spectrometry and Auger electron spectroscopy. Several routes to stabilize the random networks of copper nanowires were evaluated. Encapsulation through laminated barrier film with optical clear adhesive and atmospheric pressure spatial atomic layer deposition were found to be efficient and were used for the fabrication of transparent film heaters.

The use of Atmospheric Pressure Spatial Atomic Layer Deposition (AP-SALD) has gained popularity in the last decade. The success of this technique relies on the possibility to deposit thin films in a fast, vacuum-free, low-cost, low-damage, and high throughput way. In this work, we present ZnO and Aluminium doped ZnO (AZO) films deposited by AP-SALD at low temperature (<220 °C) with high uniformity and conformity. The ZnO films present a high transparency of 80%–90% in the visible range, with a tuneable band-gap, between 3.30 eV and 3.55 eV, controlled by the deposition temperature. The carrier density reaches values greater than 3 × 10¹⁹ cm⁻³, while the electron mobility of the films is as high as 5.5 cm² V⁻¹s⁻¹, resulting in an optimum resistivity of 5 × 10⁻² Ω cm. By doping ZnO with aluminium, the resistivity decreases down to 5.57 × 10⁻³ Ω cm, as a result of a significant increase in the carrier density up to 4.25 × 10²⁰ cm⁻³. The combination of ZnO thin films with p-type cuprous oxide (Cu₂O), deposited by aerosol assisted metal organic chemical vapor deposition, allowed the formation of oxide-based pn junctions. The dark I-V characteristic curve confirms a rectifying behaviour, opening the window for the production of all-oxide solar cells completely by chemical vapour deposition methods. We also show the potential of AP-SALD to deposit AZO as a transparent conductive oxide layer for silicon heterojunction solar cells.