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Cost-Effective and Highly Photoresponsive Nanophosphor-P3HT Photoconductive Nanocomposite for Near-Infrared Detection.

Tong Y, Zhao X, Tan MC, Zhao R - Sci Rep (2015)

Bottom Line: We seek to replace conventional expensive semiconducting photodetector materials with our cost-effective composite system.The high photocurrent measured was enabled by the unique upconversion properties of NaYF4:Yb,Er nanophosphors, where low photon energy infrared excitations are converted to high photon energy visible emissions that are later absorbed by P3HT.Our reported work lays the groundwork for the future development of printable, portable flexible and functional photonic composites for light sensing and harvesting, photonic memory devices, and phototransistors.

View Article: PubMed Central - PubMed

Affiliation: Engineering Product Development, Singapore University of Technology and Design, 8 Somapah Road, Singapore 487372.

ABSTRACT
The advent of flexible optoelectronic devices has accelerated the development of semiconducting polymeric materials. We seek to replace conventional expensive semiconducting photodetector materials with our cost-effective composite system. We demonstrate in this work the successful fabrication of a photoconductive composite film of poly(3-hexylthiophene-2,5-diyl) (P3HT) mixed with NaYF4:Yb,Er nanophosphors that exhibited a ultrahigh photoresponse to infrared radiation. The high photocurrent measured was enabled by the unique upconversion properties of NaYF4:Yb,Er nanophosphors, where low photon energy infrared excitations are converted to high photon energy visible emissions that are later absorbed by P3HT. Here we report, a significant 1.10 × 10(5) times increment of photocurrent from our photoconductive composite film upon infrared light exposure, which indicates high optical-to-electrical conversion efficiency. Our reported work lays the groundwork for the future development of printable, portable flexible and functional photonic composites for light sensing and harvesting, photonic memory devices, and phototransistors.

No MeSH data available.


Related in: MedlinePlus

(a) Photoluminescence spectrum of UCN-P3HT nanocomposite film. (b) Atomic force microscopy (AFM) image of our UCN-P3HT nanocomposite film. Scale bar, 200 nm. (c) Schematic of electronic transitions in NaYF4:Yb,Er core-shell nanoparticles upon 975 nm excitation. (d) Photograph of nanocomposite film on a flexible polyethylene terephthalate (PET) substrate.
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f2: (a) Photoluminescence spectrum of UCN-P3HT nanocomposite film. (b) Atomic force microscopy (AFM) image of our UCN-P3HT nanocomposite film. Scale bar, 200 nm. (c) Schematic of electronic transitions in NaYF4:Yb,Er core-shell nanoparticles upon 975 nm excitation. (d) Photograph of nanocomposite film on a flexible polyethylene terephthalate (PET) substrate.

Mentions: The nanocomposite film was fabricated by spin coating using a solution consisting of UCNs dispersed in a P3HT solution. The steady state emission spectrum of our nanocomposite film is shown in Fig. 2a. The intensity of green emission at 540 nm decreases relative to that of red emission at 654 nm. The integrated intensity ratio of green to red emission of our as-synthesized UCNs and nanocomposite film is shown in Supplementary Fig. 4. The green-to-red ratio decreases from 0.56 for NaYF4:Yb,Er core-shell nanoparticles to 0.23 for nanocomposite film. The observed decrease in green emission intensity is attributed to the preferred absorption of the green emission by P3HT. The surface of the obtained nanocomposite film was observed using both AFM (Fig. 2b) and SEM (Supplementary Fig. 5). The root mean square (RMS) surface roughness is estimated to be ~7.79 nm. The relatively small RMS value suggests that the surface is highly uniform. The uniform surface texture also indicates that the UCNs were homogenously dispersed within the P3HT film. The electronic transitions of our UCNs are shown in Fig. 2c. Upon NIR excitation, the Yb3+ ions absorb NIR photons through the 2F7/2 → 2F5/2 energy transition and subsequently undergo energy transfer to nearby Er3+ ions. Through energy transfer and cross-relaxation pathways, visible light is emitted through the 4S3/2 → 4I15/2 (~540 nm) and 4F9/2 → 4I15/2 (~654 nm) transitions of Er3+ ions. P3HT which has a bandgap of 1.9 eV results in corresponding absorption for wavelengths less than 650 nm. Thus, the visible emissions from our UCNs are mostly absorbed by the P3HT molecules to generate electron-hole pairs or excitons. In this composite, the long excited-state lifetime of UCNs would be most beneficial to the exciton generation process. Photocurrent is generated when a voltage bias is applied to the nanocomposite film upon exposure to NIR light. With more excitons generated, a larger photocurrent would be expected. Therefore, the performance of the photoconductor under IR light is partly dictated by the UC efficiency of our UCNs and the absorption efficiency of visible emission by the surrounding P3HT. To evaluate the possibility for making flexible device, P3HT film mixed with our UCNs was spin coated on a polyethylene terephthalate (PET) substrate as shown in Fig. 2d. By visual inspection, it is observed that our UCN-P3HT nanocomposite film adhered well with PET film and there is no visible breakage after multiple bending of the flexible substrate. The excellent adhesion demonstrates the outstanding potential of our UCN-P3HT film for flexible device fabrication. An image of flexible device is shown in Supplementary Fig. 6.


Cost-Effective and Highly Photoresponsive Nanophosphor-P3HT Photoconductive Nanocomposite for Near-Infrared Detection.

Tong Y, Zhao X, Tan MC, Zhao R - Sci Rep (2015)

(a) Photoluminescence spectrum of UCN-P3HT nanocomposite film. (b) Atomic force microscopy (AFM) image of our UCN-P3HT nanocomposite film. Scale bar, 200 nm. (c) Schematic of electronic transitions in NaYF4:Yb,Er core-shell nanoparticles upon 975 nm excitation. (d) Photograph of nanocomposite film on a flexible polyethylene terephthalate (PET) substrate.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
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getmorefigures.php?uid=PMC4645221&req=5

f2: (a) Photoluminescence spectrum of UCN-P3HT nanocomposite film. (b) Atomic force microscopy (AFM) image of our UCN-P3HT nanocomposite film. Scale bar, 200 nm. (c) Schematic of electronic transitions in NaYF4:Yb,Er core-shell nanoparticles upon 975 nm excitation. (d) Photograph of nanocomposite film on a flexible polyethylene terephthalate (PET) substrate.
Mentions: The nanocomposite film was fabricated by spin coating using a solution consisting of UCNs dispersed in a P3HT solution. The steady state emission spectrum of our nanocomposite film is shown in Fig. 2a. The intensity of green emission at 540 nm decreases relative to that of red emission at 654 nm. The integrated intensity ratio of green to red emission of our as-synthesized UCNs and nanocomposite film is shown in Supplementary Fig. 4. The green-to-red ratio decreases from 0.56 for NaYF4:Yb,Er core-shell nanoparticles to 0.23 for nanocomposite film. The observed decrease in green emission intensity is attributed to the preferred absorption of the green emission by P3HT. The surface of the obtained nanocomposite film was observed using both AFM (Fig. 2b) and SEM (Supplementary Fig. 5). The root mean square (RMS) surface roughness is estimated to be ~7.79 nm. The relatively small RMS value suggests that the surface is highly uniform. The uniform surface texture also indicates that the UCNs were homogenously dispersed within the P3HT film. The electronic transitions of our UCNs are shown in Fig. 2c. Upon NIR excitation, the Yb3+ ions absorb NIR photons through the 2F7/2 → 2F5/2 energy transition and subsequently undergo energy transfer to nearby Er3+ ions. Through energy transfer and cross-relaxation pathways, visible light is emitted through the 4S3/2 → 4I15/2 (~540 nm) and 4F9/2 → 4I15/2 (~654 nm) transitions of Er3+ ions. P3HT which has a bandgap of 1.9 eV results in corresponding absorption for wavelengths less than 650 nm. Thus, the visible emissions from our UCNs are mostly absorbed by the P3HT molecules to generate electron-hole pairs or excitons. In this composite, the long excited-state lifetime of UCNs would be most beneficial to the exciton generation process. Photocurrent is generated when a voltage bias is applied to the nanocomposite film upon exposure to NIR light. With more excitons generated, a larger photocurrent would be expected. Therefore, the performance of the photoconductor under IR light is partly dictated by the UC efficiency of our UCNs and the absorption efficiency of visible emission by the surrounding P3HT. To evaluate the possibility for making flexible device, P3HT film mixed with our UCNs was spin coated on a polyethylene terephthalate (PET) substrate as shown in Fig. 2d. By visual inspection, it is observed that our UCN-P3HT nanocomposite film adhered well with PET film and there is no visible breakage after multiple bending of the flexible substrate. The excellent adhesion demonstrates the outstanding potential of our UCN-P3HT film for flexible device fabrication. An image of flexible device is shown in Supplementary Fig. 6.

Bottom Line: We seek to replace conventional expensive semiconducting photodetector materials with our cost-effective composite system.The high photocurrent measured was enabled by the unique upconversion properties of NaYF4:Yb,Er nanophosphors, where low photon energy infrared excitations are converted to high photon energy visible emissions that are later absorbed by P3HT.Our reported work lays the groundwork for the future development of printable, portable flexible and functional photonic composites for light sensing and harvesting, photonic memory devices, and phototransistors.

View Article: PubMed Central - PubMed

Affiliation: Engineering Product Development, Singapore University of Technology and Design, 8 Somapah Road, Singapore 487372.

ABSTRACT
The advent of flexible optoelectronic devices has accelerated the development of semiconducting polymeric materials. We seek to replace conventional expensive semiconducting photodetector materials with our cost-effective composite system. We demonstrate in this work the successful fabrication of a photoconductive composite film of poly(3-hexylthiophene-2,5-diyl) (P3HT) mixed with NaYF4:Yb,Er nanophosphors that exhibited a ultrahigh photoresponse to infrared radiation. The high photocurrent measured was enabled by the unique upconversion properties of NaYF4:Yb,Er nanophosphors, where low photon energy infrared excitations are converted to high photon energy visible emissions that are later absorbed by P3HT. Here we report, a significant 1.10 × 10(5) times increment of photocurrent from our photoconductive composite film upon infrared light exposure, which indicates high optical-to-electrical conversion efficiency. Our reported work lays the groundwork for the future development of printable, portable flexible and functional photonic composites for light sensing and harvesting, photonic memory devices, and phototransistors.

No MeSH data available.


Related in: MedlinePlus