Ultrasonic Spray Pyrolysis of Antimony‐Doped Tin Oxide Transparent Conductive Coatings

Abstract

Transparent conducting oxides are fundamental for the fabrication of optoelectronic devices including touchscreen displays, solar cells, and light emitting diodes. However, they mostly rely on rare elements and expensive vacuum‐based deposition methods that negatively affect the overall cost of optoelectronics. Here, a detailed investigation on the synthesis of antimony‐doped tin oxide films using an ultrasonic spray coating system is presented. High‐quality, crystalline SnO2 films are deposited via decomposition of metal precursors sprayed directly onto hot (>400 °C) substrates. Doping is easily achieved by adding the dopant salt to the spray solution, and the presence of the dopant atoms heavily influences the optical, electrical, and structural properties of SnO2. These coatings are characterized using a comprehensive suite of techniques including X‐ray diffraction, electron microscopy, X‐ray and ultraviolet photoelectron spectroscopies, Hall effect measurements, optical spectroscopy in the visible and near infrared, and atomic force microscopy, in order to elucidate the relationship between the synthetic conditions and functional properties. Through a careful optimization process, Sb‐doped SnO2 coatings showing transmittance values in the visible spectrum between 80% and 90%, and sheet resistances of 10–20 Ω/sq−1 are achieved. Such values are suitable for immediate applications of these Sb‐doped SnO2 films as high‐performance transparent conductors.

Highly Conductive and Visibly Transparent p-Type CuCrO2 Films by Ultrasonic Spray Pyrolysis

“…Transparent electrodes, and especially transparent conducting oxides (TCOs), are fundamental components of many optoelectronic devices including solar cells, LEDs, electrochromics, and touchscreen displays because they combine high electrical conductivity and optical transparency in the visible region, making it possible for visible radiation to enter or exit the device and, at the same time, providing electrical contacts. , The majority of research on TCOs has focused mainly on n-type materials such as indium oxide doped with tin (ITO), − tin oxide doped with fluorine or antimony, − and zinc oxide doped with aluminum or gallium. − On the other hand, p-type TCOs are much less developed and studied, and they still require considerable research effort before they can become a viable industrial alternative due to their inferior electrical and optical properties. For example, Cu 2 O and Co 3 O 4 are both widely used p-type semiconductors, but they strongly absorb within the visible range (band gap energy: 2.3–2.4 eV for Cu 2 O and 2.19 eV for Co 3 O 4 ) and have lower conductivities (∼10 –6 S cm –1 for Cu 2 O and ∼10 –3 S cm –1 for Co 3 O 4 ) when compared to more established n-type TCOs. − Therefore, these optical and electrical properties are not suitable for application as transparent electrodes.…”

“…Among all the solution-based methods, ultrasonic spray pyrolysis (USP) is very attractive because it enables precise control of the deposition parameters, is suitable for large area deposition, and minimizes both material use and precursor waste. As such, USP has been employed for the deposition of both n- and p-type transparent conductive oxide layers, ,, including CuCrO 2 . ,, However, in CuCrO 2 , these spray-deposited coatings are still far inferior in terms of electrical properties when compared to vacuum-deposited coatings. The best electrical conductivity achieved for the CuCrO 2 film deposited by spray pyrolysis is ∼35 S cm –1 , but the majority of the reported values are well below 10 S cm –1 . ,,− Therefore, it is still vital to improve both the electrical and optical properties of these CuCrO 2 coatings deposited from solution-based methods to provide a viable alternative to vacuum-deposited thin films.…”

“…Among all the solution-based methods, ultrasonic spray pyrolysis (USP) is very attractive because it enables precise control of the deposition parameters, is suitable for large area deposition, and minimizes both material use and precursor waste. As such, USP has been employed for the deposition of both n-and p-type transparent conductive oxide layers, 10,11,27 including CuCrO 2 . 32,33,50 However, in CuCrO 2 , these spray-deposited coatings are still far inferior in terms of electrical properties when compared to vacuum-deposited coatings.…”

SILAR Deposition of Metal Oxide Nanostructured Films

“…Chemical deposition methods include chemical vapor deposition (CVD), anodization, electroless deposition, chemical bath deposition (CBD), successive ionic layer adsorption and reaction (SILAR), and spin/dip/spray coating or ink jet printing of sol-gel solutions or nanoparticle inks. [13][14][15][16][17][18][19][20][21][22][23][24] Atomic layer deposition (ALD) is a derivation of CVD, capable of producing highly uniform ad conformal thin films. [25][26][27][28][29] However, unlike CVD which utilizes high temperatures and a continuous flow of chemical precursors onto the substrate, ALD relies on deposition of alternating layers of precursors under controlled vacuum to obtain a homogenous and highly ordered film on the substrate.…”

Transparent electrodes based on spray coated fluorine-doped tin oxide with enhanced optical, electrical and mechanical properties

“…Top performing coatings can achieve excellent electrical (sheet resistance <20 Ω/□) and optical (visible transparency exceeding 85%) properties. 4,6,7,[9][10][11][12][13]14 Mechanical properties such as elastic modulus and hardness also play an important role in ensuring the reliability of these coatings when utilized within devices. However, only a few selected works have studied the mechanical properties of doped SnO2 thin films.…”