Transparent conductive electrodes(TCEs) are the core component used in wide variety of optoelectronic devices such as thin film transistor(TFT), touch panel screen, solar cell, etc. Among many researched materials as TCEs, the Oxide/Metal/Oxide (OMO) structured multi-layer films are promising materi...
Transparent conductive electrodes(TCEs) are the core component used in wide variety of optoelectronic devices such as thin film transistor(TFT), touch panel screen, solar cell, etc. Among many researched materials as TCEs, the Oxide/Metal/Oxide (OMO) structured multi-layer films are promising materials for flexible TCE market because of its excellent film performance for flexible TCEs as well as cost-effectiveness. When the device including OMO multilayer is used in bright environment, however, incident light can be reflected at the interface between layers that refractive indices are mismatched. As a results, the reflected light from those interfaces give films decrease of optical transmittance. Additionally, etching process of TCO film for the formation of electrode pattern can cause refractive indices mismatching between film and substrate, so it can be identified with the human eyes. In order to reduce the appearance of these fringes, there is necessary to insert additional index matching(IM) layers.
In this paper, thin silver sandwiched between manganese(4.04 at.%) doped tin oxide layers(Mn-SnO2/Ag/Mn-SnO2) were fabricated with refractive index matching layers on flexible PET substrate. To match the refractive index(n) of the Mn-SnO2/Ag/Mn-SnO2/PET film, SiO2(n=1.51)/high refractive index materials such as Mn-SnO2(n = 2.0) and TiO2(n = 2.6) were inserted between Mn-SnO2/Ag/Mn-SnO2 and PET substrate. In order to investigate the effect of IM layers, the experiment optimizing thickness of Mn-SnO2/Ag/Mn-SnO2 was performed in advance. The result suggested that optimum thickness of TCO layers exhibit 40 nm/13 nm/40 nm. For comparison and expectation of experimental results, the Essential Macleod Program(EMP) was adopted. The simulation results suggested that tendency of transmittance do not match with experimental values. However, pattern visibility characteristics such as reflectivity(ΔR550nm) and color(Δb*) matching tend to be quite similar to experimental results.
The multilayer films having optimized IM layers(SiO2(70, 80, 90 nm)/Mn-SnO2(10 nm) and SiO2(90 nm)/TiO2(10 nm)) show the excellent optical transmittance above 85 % in the 550 nm wavelength, and reduce the pattern visible defect compared to reference Mn-SnO2/Ag/Mn-SnO2/PET specimen. Both optimized films, Mn-SnO2(40 nm)/Ag(13 nm)/Mn-SnO2(40 nm)/SiO2(90 nm)/Mn-SnO2 or TiO2(10 nm), exhibit the extremely smooth surface roughness(Ra of 1.84, 2.17 nm, respectively) and quite flexible properties because there is almost no resistance change of the specimens after 10,000 cycle bending test with radius of curvature of 10 mm.
Transparent conductive electrodes(TCEs) are the core component used in wide variety of optoelectronic devices such as thin film transistor(TFT), touch panel screen, solar cell, etc. Among many researched materials as TCEs, the Oxide/Metal/Oxide (OMO) structured multi-layer films are promising materials for flexible TCE market because of its excellent film performance for flexible TCEs as well as cost-effectiveness. When the device including OMO multilayer is used in bright environment, however, incident light can be reflected at the interface between layers that refractive indices are mismatched. As a results, the reflected light from those interfaces give films decrease of optical transmittance. Additionally, etching process of TCO film for the formation of electrode pattern can cause refractive indices mismatching between film and substrate, so it can be identified with the human eyes. In order to reduce the appearance of these fringes, there is necessary to insert additional index matching(IM) layers.
In this paper, thin silver sandwiched between manganese(4.04 at.%) doped tin oxide layers(Mn-SnO2/Ag/Mn-SnO2) were fabricated with refractive index matching layers on flexible PET substrate. To match the refractive index(n) of the Mn-SnO2/Ag/Mn-SnO2/PET film, SiO2(n=1.51)/high refractive index materials such as Mn-SnO2(n = 2.0) and TiO2(n = 2.6) were inserted between Mn-SnO2/Ag/Mn-SnO2 and PET substrate. In order to investigate the effect of IM layers, the experiment optimizing thickness of Mn-SnO2/Ag/Mn-SnO2 was performed in advance. The result suggested that optimum thickness of TCO layers exhibit 40 nm/13 nm/40 nm. For comparison and expectation of experimental results, the Essential Macleod Program(EMP) was adopted. The simulation results suggested that tendency of transmittance do not match with experimental values. However, pattern visibility characteristics such as reflectivity(ΔR550nm) and color(Δb*) matching tend to be quite similar to experimental results.
The multilayer films having optimized IM layers(SiO2(70, 80, 90 nm)/Mn-SnO2(10 nm) and SiO2(90 nm)/TiO2(10 nm)) show the excellent optical transmittance above 85 % in the 550 nm wavelength, and reduce the pattern visible defect compared to reference Mn-SnO2/Ag/Mn-SnO2/PET specimen. Both optimized films, Mn-SnO2(40 nm)/Ag(13 nm)/Mn-SnO2(40 nm)/SiO2(90 nm)/Mn-SnO2 or TiO2(10 nm), exhibit the extremely smooth surface roughness(Ra of 1.84, 2.17 nm, respectively) and quite flexible properties because there is almost no resistance change of the specimens after 10,000 cycle bending test with radius of curvature of 10 mm.
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#TCO OMO multilayer Refractive index matching layer
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