Limits...
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

Electrical characteristics of photoconductors formed using the UCN-P3HT nanocomposite film.(a) I–V curve of photoconductor under illumination of a 975 nm laser pen. (b,c) Linear and log scale I–V curves of photocurrent under excitation of 975 nm laser with various power intensities. It shows a 1.1 × 105 increment of photocurrent. (d,e) Linear and log scale I–V curves of photocurrent under excitation of 808 nm laser with various power intensities. It shows a 0.8 × 105 increment of photocurrent. (f) Potential dependence of the increment of the photocurrent for 975 nm laser. (g) Potential dependence of the increment of the photocurrent for 808 nm laser.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f4: Electrical characteristics of photoconductors formed using the UCN-P3HT nanocomposite film.(a) I–V curve of photoconductor under illumination of a 975 nm laser pen. (b,c) Linear and log scale I–V curves of photocurrent under excitation of 975 nm laser with various power intensities. It shows a 1.1 × 105 increment of photocurrent. (d,e) Linear and log scale I–V curves of photocurrent under excitation of 808 nm laser with various power intensities. It shows a 0.8 × 105 increment of photocurrent. (f) Potential dependence of the increment of the photocurrent for 975 nm laser. (g) Potential dependence of the increment of the photocurrent for 808 nm laser.

Mentions: For the photoconductor fabricated using the composite film, we measured the electrical characteristics of the devices under the illumination of lasers at different wavelength. Figure 4a shows the current-voltage (I-V) characteristics of the photoconductor under the illumination of a 975 nm wavelength laser pen. It is clearly observed that illumination at 975 nm leads to a considerable photocurrent increase of ~3.5 orders when compared to dark current. The significant enhancement can be attributed to the enhanced absorption and conversion of our UCN-P3HT nanocomposite film, where the efficiency of the UC emission processes of NaYF4:Yb,Er nanophosphors was a critical determinant. The sudden change of photocurrent at −1.5 V is caused by shaking of laser pen. The encouraging results that are obtained for the first-time for solution-processed photoconductions inspired further studies using excitation sources at other wavelengths (i.e. 975 nm and 808 nm) and power intensities using our photoconductors. In Fig. 4b and c, it was found that the photocurrent increased with the increase of the 975 nm laser power. A significant ~1.10 × 105 times increment of photocurrent was achieved at the maximum illumination power (i.e. 13.4 W/cm2) using the 975 nm laser source. Compared to the results reported in the literature, this is a ~2.75 × 104 times enhancement in terms of the increment of the photocurrent under the illumination of laser47. To examine the response of the photocurrent to incident laser power, the responsivity Ri of the photoconductor is calculated as Ri = Iphoto/Pin, where Iphoto is the photocurrent and Pin is the incident laser power. A responsivity of 7.6 A/W can be obtained from the photoconductor under an applied bias voltage of 3 V with 975 nm laser illumination of 0.1 W/cm2. This significant increase of photocurrent should be ascribed to the high upconversion efficiency of the as-synthesized UCNs whose decay time (~0.44 ms) is more than two times higher than the value (~0.20 ms) reported in the literature47 and the high loading (10 vol%) of UCNs in P3HT film. Both the high upconversion efficiency and high loading of UCNs provides much brighter visible emissions under the illumination of a 975 nm wavelength laser which can be subsequently absorbed by P3HT film to generate more electron-hole pairs or excitons. Thus large photocurrent increment can be observed when a voltage bias is applied. The large photocurrent increment further ascertains the compelling potential of using the nanocomposite film demonstrated in this work to advance the design of flexible optoelectronic devices. For measurements made using the 808 nm laser as shown in Fig. 4d and e, an obvious ~0.82 × 105 times increment of photocurrent was found as well. A responsivity of 0.96 A/W can be obtained from the photoconductor under an applied bias voltage of 3 V with 808 nm laser illumination of 0.5 W/cm2. The increment would be associated to the optical characteristics of our UCNs, where NaYF4:Yb,Er nanophosphors exhibit a response upon excitation at both 975 and 808 nm. External quantum efficiency (EQE) which is defined as the number of electrons detected per incident photon can be expressed as hcRi/(eλ), where h is the Plank’s constant, c is the velocity of light, e is the electronic charge, λ is the excitation wavelength. EQE for the photoconductor at a bias of 3 V has been calculated as 966% and 122% for 975 nm laser illumination of 0.1 W/cm2 and 808 nm laser illumination of 0.5 W/cm2, respectively. It should be noted that our 975 nm laser source has a lower output power than that of the 808 nm laser source although the supplied current to the laser drivers is maintained at the same value, e.g. 3.5 A during the experiments. However, a higher photocurrent was measured upon illumination using the 975 nm laser than that of the 808 nm laser (at the same current). The higher photocurrent measured at 975 nm suggests that our nanocomposite film was more responsive and sensitive to the 975 nm laser compared to that of the 808 nm laser. Next, the effect of potential difference on the increment of photocurrent (i.e. Iphoto − Idark) was investigated for both 975 nm and 808 nm lasers as shown in Fig. 4f and g. It was found that the increment of photocurrent became noticeably larger as the applied voltage on photoconductor increased. In addition, the saturation of photocurrent was not reached when the power intensity was at a maximum for both laser sources at 975 and 808 nm. Since photocurrent saturation has not been reached, the full potential of our UCN-P3HT nanocomposite film as a photoconductor has not been realized and a further enhancement can be expected at higher laser powers. The electrical characteristics of flexible devices are shown in Supplementary Fig. S7.


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

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

Electrical characteristics of photoconductors formed using the UCN-P3HT nanocomposite film.(a) I–V curve of photoconductor under illumination of a 975 nm laser pen. (b,c) Linear and log scale I–V curves of photocurrent under excitation of 975 nm laser with various power intensities. It shows a 1.1 × 105 increment of photocurrent. (d,e) Linear and log scale I–V curves of photocurrent under excitation of 808 nm laser with various power intensities. It shows a 0.8 × 105 increment of photocurrent. (f) Potential dependence of the increment of the photocurrent for 975 nm laser. (g) Potential dependence of the increment of the photocurrent for 808 nm laser.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4645221&req=5

f4: Electrical characteristics of photoconductors formed using the UCN-P3HT nanocomposite film.(a) I–V curve of photoconductor under illumination of a 975 nm laser pen. (b,c) Linear and log scale I–V curves of photocurrent under excitation of 975 nm laser with various power intensities. It shows a 1.1 × 105 increment of photocurrent. (d,e) Linear and log scale I–V curves of photocurrent under excitation of 808 nm laser with various power intensities. It shows a 0.8 × 105 increment of photocurrent. (f) Potential dependence of the increment of the photocurrent for 975 nm laser. (g) Potential dependence of the increment of the photocurrent for 808 nm laser.
Mentions: For the photoconductor fabricated using the composite film, we measured the electrical characteristics of the devices under the illumination of lasers at different wavelength. Figure 4a shows the current-voltage (I-V) characteristics of the photoconductor under the illumination of a 975 nm wavelength laser pen. It is clearly observed that illumination at 975 nm leads to a considerable photocurrent increase of ~3.5 orders when compared to dark current. The significant enhancement can be attributed to the enhanced absorption and conversion of our UCN-P3HT nanocomposite film, where the efficiency of the UC emission processes of NaYF4:Yb,Er nanophosphors was a critical determinant. The sudden change of photocurrent at −1.5 V is caused by shaking of laser pen. The encouraging results that are obtained for the first-time for solution-processed photoconductions inspired further studies using excitation sources at other wavelengths (i.e. 975 nm and 808 nm) and power intensities using our photoconductors. In Fig. 4b and c, it was found that the photocurrent increased with the increase of the 975 nm laser power. A significant ~1.10 × 105 times increment of photocurrent was achieved at the maximum illumination power (i.e. 13.4 W/cm2) using the 975 nm laser source. Compared to the results reported in the literature, this is a ~2.75 × 104 times enhancement in terms of the increment of the photocurrent under the illumination of laser47. To examine the response of the photocurrent to incident laser power, the responsivity Ri of the photoconductor is calculated as Ri = Iphoto/Pin, where Iphoto is the photocurrent and Pin is the incident laser power. A responsivity of 7.6 A/W can be obtained from the photoconductor under an applied bias voltage of 3 V with 975 nm laser illumination of 0.1 W/cm2. This significant increase of photocurrent should be ascribed to the high upconversion efficiency of the as-synthesized UCNs whose decay time (~0.44 ms) is more than two times higher than the value (~0.20 ms) reported in the literature47 and the high loading (10 vol%) of UCNs in P3HT film. Both the high upconversion efficiency and high loading of UCNs provides much brighter visible emissions under the illumination of a 975 nm wavelength laser which can be subsequently absorbed by P3HT film to generate more electron-hole pairs or excitons. Thus large photocurrent increment can be observed when a voltage bias is applied. The large photocurrent increment further ascertains the compelling potential of using the nanocomposite film demonstrated in this work to advance the design of flexible optoelectronic devices. For measurements made using the 808 nm laser as shown in Fig. 4d and e, an obvious ~0.82 × 105 times increment of photocurrent was found as well. A responsivity of 0.96 A/W can be obtained from the photoconductor under an applied bias voltage of 3 V with 808 nm laser illumination of 0.5 W/cm2. The increment would be associated to the optical characteristics of our UCNs, where NaYF4:Yb,Er nanophosphors exhibit a response upon excitation at both 975 and 808 nm. External quantum efficiency (EQE) which is defined as the number of electrons detected per incident photon can be expressed as hcRi/(eλ), where h is the Plank’s constant, c is the velocity of light, e is the electronic charge, λ is the excitation wavelength. EQE for the photoconductor at a bias of 3 V has been calculated as 966% and 122% for 975 nm laser illumination of 0.1 W/cm2 and 808 nm laser illumination of 0.5 W/cm2, respectively. It should be noted that our 975 nm laser source has a lower output power than that of the 808 nm laser source although the supplied current to the laser drivers is maintained at the same value, e.g. 3.5 A during the experiments. However, a higher photocurrent was measured upon illumination using the 975 nm laser than that of the 808 nm laser (at the same current). The higher photocurrent measured at 975 nm suggests that our nanocomposite film was more responsive and sensitive to the 975 nm laser compared to that of the 808 nm laser. Next, the effect of potential difference on the increment of photocurrent (i.e. Iphoto − Idark) was investigated for both 975 nm and 808 nm lasers as shown in Fig. 4f and g. It was found that the increment of photocurrent became noticeably larger as the applied voltage on photoconductor increased. In addition, the saturation of photocurrent was not reached when the power intensity was at a maximum for both laser sources at 975 and 808 nm. Since photocurrent saturation has not been reached, the full potential of our UCN-P3HT nanocomposite film as a photoconductor has not been realized and a further enhancement can be expected at higher laser powers. The electrical characteristics of flexible devices are shown in Supplementary Fig. S7.

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