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Tuning the peak position of subwavelength silica nanosphere broadband antireflection coatings.

Tao F, Hiralal P, Ren L, Wang Y, Dai Q, Amaratunga GA, Zhou H - Nanoscale Res Lett (2014)

Bottom Line: Subwavelength nanostructures are considered as promising building blocks for antireflection and light trapping applications.The tunable optical transmission peaks of the Langmuir-Blodgett films were correlated with deposition parameters such as surface pressure, surfactant concentration, ageing of suspensions and annealing effect.Such peak-tunable broadband antireflection coating has wide applications in diversified industries such as solar cells, windows, displays and lenses.

View Article: PubMed Central - HTML - PubMed

Affiliation: School of Electronic and Computer Engineering, Peking University Shenzhen Graduate School, 2199 Lishui Road, Shenzhen, Guangdong 518055, China.

ABSTRACT
Subwavelength nanostructures are considered as promising building blocks for antireflection and light trapping applications. In this study, we demonstrate excellent broadband antireflection effect from thin films of monolayer silica nanospheres with a diameter of 100 nm prepared by Langmuir-Blodgett method on glass substrates. With a single layer of compact silica nanosphere thin film coated on both sides of a glass, we achieved maximum transmittance of 99% at 560 nm. Furthermore, the optical transmission peak of the nanosphere thin films can be tuned over the UV-visible range by changing processing parameters during Langmuir-Blodgett deposition. The tunable optical transmission peaks of the Langmuir-Blodgett films were correlated with deposition parameters such as surface pressure, surfactant concentration, ageing of suspensions and annealing effect. Such peak-tunable broadband antireflection coating has wide applications in diversified industries such as solar cells, windows, displays and lenses.

No MeSH data available.


Related in: MedlinePlus

Transmission spectra. (a) AR films deposited at different pressures. (b) AR films deposited from fresh suspension with 1.0 mM, fresh suspension with 1.9 mM CTAB concentration and ageing suspension with 1.9 mM CTAB.
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Figure 3: Transmission spectra. (a) AR films deposited at different pressures. (b) AR films deposited from fresh suspension with 1.0 mM, fresh suspension with 1.9 mM CTAB concentration and ageing suspension with 1.9 mM CTAB.

Mentions: The influence of surface pressure during deposition on the transmission of the samples was investigated. Surface pressure of the mixed liquid is determined by the interaction between nanospheres. Surface pressure πA is given by equation πA = γ0 - γ, where γ0 is equal to the surface tension of the water and γ is the surface tension of water with monolayer nanospheres. When the nanospheres are sufficiently far from each other, the resulting surface pressure is therefore very low, with measured pressure values similar to the pressure of pure water (γ = 71.97 mN/m at 25°C). When the average distance between spheres was reduced due to compression, surface pressure increased rapidly as a result of the strong interaction between spheres, i.e. adding a monolayer to the surface reduces the surface tension (γ < γ0). Further compression would cause monolayer collapse, forming nanosphere aggregations. Surface pressure just before the collapse of monolayer is known as collapse pressure. Collapse pressure of silica nanospheres in this experiment was 19 mN/m. Deposition pressures both under and above collapse pressure were studied. Figure 3a shows the transmission spectra of glass coated with AR films deposited at five different pressures. The pressures of 22.2 and 28 mN/m are both higher than collapse pressure, whereas all other three pressures are lower than collapse pressure. Three distinct peaks can be seen in the figure (468, 517 and 581 nm). Transmission peak was the same for samples deposited with pressures below collapse pressure (i.e. p = 7.8, 12.4 and 18.5 mN/m), while for samples deposited above this value (p = 22.2 and 28.0 mN/m), a shift in peak transmission position, which is a function of deposition pressure, was shown. For samples deposited below collapse pressure, the same spectral peak indicates that they are all thin films with monolayer nanospheres. The sample deposited at 7.8 mN/m had lower transmittance than the other two samples in long wavelength range, which may be due to the lower coverage of nanospheres on plain glass. We suspect that nanosphere aggregations formed when pressure went higher than collapse pressure, which caused the shift of transmission peak. Thus, samples deposited at p= 22.2 and 28.0 mN/m were nanospheres with different aggregation degrees rather than monolayer film of nanospheres.


Tuning the peak position of subwavelength silica nanosphere broadband antireflection coatings.

Tao F, Hiralal P, Ren L, Wang Y, Dai Q, Amaratunga GA, Zhou H - Nanoscale Res Lett (2014)

Transmission spectra. (a) AR films deposited at different pressures. (b) AR films deposited from fresh suspension with 1.0 mM, fresh suspension with 1.9 mM CTAB concentration and ageing suspension with 1.9 mM CTAB.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4128290&req=5

Figure 3: Transmission spectra. (a) AR films deposited at different pressures. (b) AR films deposited from fresh suspension with 1.0 mM, fresh suspension with 1.9 mM CTAB concentration and ageing suspension with 1.9 mM CTAB.
Mentions: The influence of surface pressure during deposition on the transmission of the samples was investigated. Surface pressure of the mixed liquid is determined by the interaction between nanospheres. Surface pressure πA is given by equation πA = γ0 - γ, where γ0 is equal to the surface tension of the water and γ is the surface tension of water with monolayer nanospheres. When the nanospheres are sufficiently far from each other, the resulting surface pressure is therefore very low, with measured pressure values similar to the pressure of pure water (γ = 71.97 mN/m at 25°C). When the average distance between spheres was reduced due to compression, surface pressure increased rapidly as a result of the strong interaction between spheres, i.e. adding a monolayer to the surface reduces the surface tension (γ < γ0). Further compression would cause monolayer collapse, forming nanosphere aggregations. Surface pressure just before the collapse of monolayer is known as collapse pressure. Collapse pressure of silica nanospheres in this experiment was 19 mN/m. Deposition pressures both under and above collapse pressure were studied. Figure 3a shows the transmission spectra of glass coated with AR films deposited at five different pressures. The pressures of 22.2 and 28 mN/m are both higher than collapse pressure, whereas all other three pressures are lower than collapse pressure. Three distinct peaks can be seen in the figure (468, 517 and 581 nm). Transmission peak was the same for samples deposited with pressures below collapse pressure (i.e. p = 7.8, 12.4 and 18.5 mN/m), while for samples deposited above this value (p = 22.2 and 28.0 mN/m), a shift in peak transmission position, which is a function of deposition pressure, was shown. For samples deposited below collapse pressure, the same spectral peak indicates that they are all thin films with monolayer nanospheres. The sample deposited at 7.8 mN/m had lower transmittance than the other two samples in long wavelength range, which may be due to the lower coverage of nanospheres on plain glass. We suspect that nanosphere aggregations formed when pressure went higher than collapse pressure, which caused the shift of transmission peak. Thus, samples deposited at p= 22.2 and 28.0 mN/m were nanospheres with different aggregation degrees rather than monolayer film of nanospheres.

Bottom Line: Subwavelength nanostructures are considered as promising building blocks for antireflection and light trapping applications.The tunable optical transmission peaks of the Langmuir-Blodgett films were correlated with deposition parameters such as surface pressure, surfactant concentration, ageing of suspensions and annealing effect.Such peak-tunable broadband antireflection coating has wide applications in diversified industries such as solar cells, windows, displays and lenses.

View Article: PubMed Central - HTML - PubMed

Affiliation: School of Electronic and Computer Engineering, Peking University Shenzhen Graduate School, 2199 Lishui Road, Shenzhen, Guangdong 518055, China.

ABSTRACT
Subwavelength nanostructures are considered as promising building blocks for antireflection and light trapping applications. In this study, we demonstrate excellent broadband antireflection effect from thin films of monolayer silica nanospheres with a diameter of 100 nm prepared by Langmuir-Blodgett method on glass substrates. With a single layer of compact silica nanosphere thin film coated on both sides of a glass, we achieved maximum transmittance of 99% at 560 nm. Furthermore, the optical transmission peak of the nanosphere thin films can be tuned over the UV-visible range by changing processing parameters during Langmuir-Blodgett deposition. The tunable optical transmission peaks of the Langmuir-Blodgett films were correlated with deposition parameters such as surface pressure, surfactant concentration, ageing of suspensions and annealing effect. Such peak-tunable broadband antireflection coating has wide applications in diversified industries such as solar cells, windows, displays and lenses.

No MeSH data available.


Related in: MedlinePlus