High-Work-Function Transparent Conductive Oxides with Multilayer Films

Abstract

Transparent conductive oxide (TCO) films using WO3/Ag/WO3 (WAW) were fabricated under room temperature conditions. WAW has a low sheet resistance of 12 Ω/sq and a work function of 6.334 eV. This is one of the TCOs with the highest work function. These properties make it useful for application in electroluminescent devices and solar cells. Both theoretical calculation and experimental results show that the two WO3 layers strongly affect transparency, while the Ag layer determines transmittance and electrical performances. These rules can be applied in all dielectric/metal/dielectric structures.

Silicon based solar cells using a multilayer oxide as emitter

“…Increase the thickness of top WO 3 layer from 30 nm to 80 nm, the transmittance peaks of WAW multilayer would demonstrate red-shift due to light coupling. 23 Since the transmitted photons are absorbed by n-type silicon underneath WAW multilayer to generate current, the EQE curves are red-shifted. The red-shift of reflectance peaks are expected to better match the AM 1.5G spectrum, which has the maximum photon flux in 600 nm 33 (as depicted in Fig.…”

“…For intermediate Ag layer, the deposition pressure was kept at 8.0 × 10 −4 Pa. For both WO 3 layers, O 2 gas was introduced to ensure that the vacuum pressure was 1.5∼2.5 × 10 −2 Pa, detailed procedure could be found in Ref. 23. The front electrode was fabricated by depositing 500-nm-thick Ag through a shadow mask, and 500 nm Ag film was evaporated onto the rear side of the silicon as electrode.…”

“…Compared with MAM and VAV, WAW multilayer is more transparent and environmentally friendly. What's more, high work-function of 6.334 eV has been reported for WAW multilayer, 23 which is the key factor for hole-selectivity contact. In this work, we develop a novel solar cell structure using WAW multilayer as emitter on n-type silicon (WAW/n-Si solar cells), neither any TCO film nor any post-deposition annealing is employed in device fabrication process.…”

Effect of W–Ti target composition on the surface chemistry and electronic structure of WO3–TiO2 films made by reactive sputtering

“…Tungsten oxide (WO 3 ) is a widely studied "chromogenic" material with interesting structural, electronic and optical properties for utilization in many scientific and technological applications [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15]. Among metal oxide semiconductors, WO 3 has become a focal point of interest where nanostructured and low-dimensional forms of WO 3 are beneficial for technological development.…”

“…WO 3 thin films and nanostructures exhibit an optical band gap (~2.4-3.2 eV, depending on processing conditions) that permits efficient use of the solar spectrum including absorption in the blue part of the visible region and the ultraviolet region, as well as a high transmission region that extends from the near-infrared (IR) to the visible spectrum [1][2][3][4]. Coupled with good electronic transport properties, photosensitivity, and chemical integrity, WO 3 -based materials are attractive for applications related to sustainable energy production including energy efficient windows and architecture, photoelectrochemical water-splitting, photocatalysis and solar cells [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16]. While WO 3 photo-catalysts find many interesting industrial applications, their photocatalytic and electronic properties are highly influenced by the structure and composition [16].…”