Can fluorine-doped tin Oxide, FTO, be more like indium-doped tin oxide, ITO? Reducing FTO surface roughness by introduci
- PDF / 419,055 Bytes
- 5 Pages / 612 x 792 pts (letter) Page_size
- 97 Downloads / 227 Views
Research Letter
Can fluorine-doped tin Oxide, FTO, be more like indium-doped tin oxide, ITO? Reducing FTO surface roughness by introducing additional SnO2 coating David A. Keller, Hannah-Noa Barad, Eli Rosh-Hodesh, Arie Zaban, and David Cahen, Department of Chemistry, Center for Nanotechnology & Advanced Materials, Bar Ilan University, 5290002 Ramat Gan, Israel Address all correspondence to David A. Keller at [email protected] (Received 5 July 2018; accepted 15 August 2018)
Abstract Among the commercially common transparent conducting oxides (TCOs) are fluorine-doped tin oxide (FTO) and indium-doped tin oxide (ITO), neither of which meets all criteria for the optimal TCO. Despite its superior chemical stability and being composed of abundant elements, FTO suffers from high surface roughness compared to ITO. Here, we introduce a path to substantially decrease the surface roughness of FTO, while preserving most of its original advantages, by depositing an SnO2 coating on top of the FTO layer using pulsed laser deposition. Such an enhancement may allow future use of FTO in devices that use now the more expensive, less stable ITO, which contains relatively rare indium.
Introduction Transparent conducting oxides (TCOs) are necessary components in many optoelectronic systems, including various renewable energy devices, electrochromic windows, and flat-panel displays.[1] Due to the increasing demand for TCOs, significant attempts have been made to find new materials that can serve as TCOs as well as optimize the existing materials.[2] Among the prevailing TCOs, the vast majority are based on SnO2, ZnO, and In2O3, usually containing various dopants.[3] Two of the most common commercial TCOs are fluorine-doped tin oxide (FTO) and indium tin oxide (ITO).[4] As expressed by the term transparent conducting oxide, the main requirements for a TCO are[5]: • High optical transparency (>75%)[4] • Adequate electrical conductivity (ρ < 1 × 10−2 Ω cm)[4] However, three additional requirements need to be fulfilled when looking for the ideal TCO: • Excellent chemical and thermal stability that will allow the TCO to maintain its physical properties during possibly difficult fabrication and operation conditions[2]; • High abundance of each of the constituent chemical elements[6]; • Minimal surface roughness, i.e., smoother morphology and smaller particles on the surface. Currently, ITO is the TCO with the lower surface roughness, with an Ra of ∼1–2 nm.[7] A rough surface complicates electrical contact with the adjacent layer, and can result in poor or erratic electrical transport at the interface, increases the chance
of forming electrical shorts, and increases the scattering of light, which lowers optical specular transmission.[8] The two common commercial products, FTO and ITO, do not meet all TCO criteria mentioned above. Both materials demonstrate sufficient transparency and electrical conductivity.[9] However, FTO is much more stable than ITO. For example, its optical and electrical properties can be maintained for temperatures up to ∼60
Data Loading...
