OSA's Digital Library

Optics Express

Optics Express

  • Editor: C. Martijn de Sterke
  • Vol. 20, Iss. 22 — Oct. 22, 2012
  • pp: 25071–25076
« Show journal navigation

Fabrication of high color rendering index white LED using Cd-free wavelength tunable Zn doped CuInS2 nanocrystals

Wonkeun Chung, Hyunchul Jung, Chang Hun Lee, and Sung Hyun Kim  »View Author Affiliations


Optics Express, Vol. 20, Issue 22, pp. 25071-25076 (2012)
http://dx.doi.org/10.1364/OE.20.025071


View Full Text Article

Acrobat PDF (2138 KB)





Browse Journals / Lookup Meetings

Browse by Journal and Year


   


Lookup Conference Papers

Close Browse Journals / Lookup Meetings

Article Tools

Share
Citations

Abstract

Highly luminescent Cd–free Zn doped CuInS2 nanocrystals (ZCIS NCs) were synthesized, and their properties were evaluated using X-ray diffraction, Raman, UV, and photoluminescence. The crystal structure of the ZCIS NCs was similar to the zinc blende, and the lattice constant decreased with increasing Zn concentration. By incorporation of Zn, the emission wavelength was tuned from 536 to 637nm with concomitant enhancement of the quantum yield up to 45%. A white light emitting diodes, integrating dual ZCIS NCs (λem = 567, and 617nm) and a 460nm InGaN LED, exhibited a high color rendering index of 84.1 with a warm color temperature of 4256.2K. The CIE-1931 chromaticity coordinates were slightly shifted from (0.3626, 0.3378) at 20mA to (0.3480, 0.3206) at 50mA.

© 2012 OSA

1. Introduction

Semiconductor nanocrystals (NCs) exhibit the unique properties of tunable band gap, broad absorption, and photostability, making them highly attractive materials for a wide cross-section of applications. Semiconductor NCs became potential alternatives for use in light emitting diodes (LED), solar cell, and bio-imaging [1

1. V. Colvin, M. Schlamp, and A. Alivisatos, “Light-emitting diodes made from cadmium selenide nanocrystals and a semiconducting polymer,” Nature 370(6488), 354–357 (1994). [CrossRef]

4

4. W. C. Chan and S. Nie, “Quantum dot bioconjugates for ultrasensitive nonisotopic detection,” Science 281(5385), 2016–2018 (1998). [CrossRef] [PubMed]

]. Research regarding NCs for color conversion in white LED has been particularly highlighted because of the tunability of the emission of these NCs over the entire visible region, their high quantum yield, and their facile fabrication.

Following the initial suggestion of CdSe NC-based color conversion LED by Klimov et al. [5

5. M. Achermann, M. A. Petruska, S. Kos, D. L. Smith, D. D. Koleske, and V. I. Klimov, “Energy-transfer pumping of semiconductor nanocrystals using an epitaxial quantum well,” Nature 429(6992), 642–646 (2004). [CrossRef] [PubMed]

], similar types of white LED have been widely explored for improving the quality of white light [6

6. H. Chen, C. Hsu, and H. Hong, “InGaN–CdSe–ZnSe quantum dots white LEDs,” IEEE Photon. Technol. Lett. 18(1), 193–195 (2006). [CrossRef]

10

10. E. Jang, S. Jun, H. Jang, J. Lim, B. Kim, and Y. Kim, “White-light-emitting diodes with quantum dot color converters for display backlight,” Adv. Mater. (Deerfield Beach Fla.) 22(28), 3076–3080 (2010). [CrossRef]

]. Chen et al. developed a white LED consisting of a CdSe/ZnSe NCs convertor pumped by a blue InGaN LED [6

6. H. Chen, C. Hsu, and H. Hong, “InGaN–CdSe–ZnSe quantum dots white LEDs,” IEEE Photon. Technol. Lett. 18(1), 193–195 (2006). [CrossRef]

]. Demir et al. controlled the color rendering index (CRI) and color temperature of white light using a combination of various emissions of CdSe NCs [7

7. S. Nizamoglu, T. Ozel, E. Sari, and H. Demir, “White light generation using CdSe/ZnS core–shell nanocrystals hybridized with InGaN/GaN light emitting diodes,” Nanotechnology 18(6), 065709 (2007). [CrossRef]

, 8

8. S. Nizamoglu, G. Zengin, and H. Demir, “Color-converting combinations of nanocrystal emitters for warm-white light generation with high color rendering index,” Appl. Phys. Lett. 92(3), 031102 (2008). [CrossRef]

]; recently, Jang et al. fabricated a 41 lm/W white LED with a color temperature of 100,000 K for display backlighting using a multi-core–shell CdSe NCs structure [10

10. E. Jang, S. Jun, H. Jang, J. Lim, B. Kim, and Y. Kim, “White-light-emitting diodes with quantum dot color converters for display backlight,” Adv. Mater. (Deerfield Beach Fla.) 22(28), 3076–3080 (2010). [CrossRef]

].

However, the inherent toxicity of Cd makes its use undesirable in terms of human and environmental impacts, thus limiting the practical application of Cd-based LED. Cd-free CuInS2 semiconductor NCs are regarded as viable alternatives due to their direct band gap (1.5 eV), and large absorption coefficient. The band gap can also be tuned by particle size [11

11. S. Castro, S. Bailey, R. Raffaelle, K. Banger, and A. Hepp, “Synthesis and characterization of colloidal CuInS2 nanoparticles from a molecular single-source precursor,” J. Phys. Chem. B 108(33), 12429–12435 (2004). [CrossRef]

, 12

12. L. Li, T. Daou, I. Texier, T. Chi, N. Liem, and P. Reiss, “Highly luminescent CuInS2/ZnS core/shell nanocrystals:cadmium-free quantum dots for in vivo imaging,” Chem. Mater. 21(12), 2422–2429 (2009). [CrossRef]

], composite [13

13. M. Uehara, K. Watanabe, Y. Tajiri, H. Nakamura, and H. Maeda, “Synthesis of CuInS2 fluorescent nanocrystals and enhancement of fluorescence by controlling crystal defect,” J. Chem. Phys. 129(13), 134709 (2008). [CrossRef] [PubMed]

], or by alloying with ZnS [14

14. H. Nakamura, W. Kato, M. Uehara, K. Nose, T. Omata, S. Matsuo, M. Miyazaki, and H. Maeda, “Tunable photoluminescence wavelength of chalcopyrite CuInS2-based semiconductor nanocrystals synthesized in a colloidal system,” Chem. Mater. 18(14), 3330–3335 (2006). [CrossRef]

16

16. J. Feng, M. Sun, F. Yang, and X. Yang, “A facile approach to synthesize high-quality ZnxCuyInS1.5+x+0.5y nanocrystal emitters,” Chem. Commun. (Camb.) 47(22), 6422–6424 (2011). [CrossRef] [PubMed]

]. Castro et al. synthesized CuInS2 NCs by decomposition of single source precursors [11

11. S. Castro, S. Bailey, R. Raffaelle, K. Banger, and A. Hepp, “Synthesis and characterization of colloidal CuInS2 nanoparticles from a molecular single-source precursor,” J. Phys. Chem. B 108(33), 12429–12435 (2004). [CrossRef]

], and Nakamura et al. enhanced the quantum yield of these NCs by doping Zn ions into the CuInS2 [14

14. H. Nakamura, W. Kato, M. Uehara, K. Nose, T. Omata, S. Matsuo, M. Miyazaki, and H. Maeda, “Tunable photoluminescence wavelength of chalcopyrite CuInS2-based semiconductor nanocrystals synthesized in a colloidal system,” Chem. Mater. 18(14), 3330–3335 (2006). [CrossRef]

]. Reiss and associates further improved the quantum yield by using dodecanethiol as a sulfur source and stabilizing ligand [12

12. L. Li, T. Daou, I. Texier, T. Chi, N. Liem, and P. Reiss, “Highly luminescent CuInS2/ZnS core/shell nanocrystals:cadmium-free quantum dots for in vivo imaging,” Chem. Mater. 21(12), 2422–2429 (2009). [CrossRef]

], and Xie’s group demonstrated highly luminescent CuZnInS NCs without shell coatings [15

15. J. Zhang, R. Xie, and W. Yang, “A simple route for highly luminescent quaternary Cu-Zn-In-S nanocrystal emitter,” Chem. Mater. 23(14), 3357–3361 (2011). [CrossRef]

]. However, despite the suitability of properties, the application of CuInS2 NCs was limited to employing red color convertor for white LED [17

17. H. Kim, B. Kwon, M. Suh, D. Kang, Y. Kim, and D. Jeon, “Degradation characteristics of red light-emitting CuInS2/ZnS quantum dots as a wavelength converter for LEDs,” Electrochem. Solid-State Lett. 14(10), K55–K57 (2011). [CrossRef]

, 18

18. W. Chung, H. Jung, C. Lee, S. Park, J. Kim, and S. Kim, “Synthesis and application of non-toxic ZnCuInS2/ZnS nanocrystals for white LED by hybridization with conjugated polymer,” J. Electrochem. Soc. 158(12), H1218–H1220 (2011). [CrossRef]

].

In this study, yellow to red color tunable strongly luminescent ZnCuInS (ZCIS) NCs were prepared by a simple synthetic method, and were employed in a color convertor for white LED. The emission wavelength was tuned by introducing different molar ratio of Zn, and corresponding structural and optical properties were investigated by X-ray diffraction (XRD), Raman, and Photoluminescence (PL). A white LED was fabricated by integrating a blue InGaN LED with yellow and red emitting quaternary ZCIS NCs, and the characteristics were examined.

2. Experimental

3. Results and discussion

Figure 1
Fig. 1 The Powder X-ray diffraction patterns of ZnCuInS nanocrystals with different Cu( = In):Zn ratios.
shows the powder XRD patterns (Philips XPERT MPD) of the ZCIS NCs with various Cu( = In)/Zn ratios. The diffraction patterns were broadened which was indicative of nano-sized particles, and three apparent peaks were observed corresponding to the (1 2 2)/(1 0 3), (2 2 0), and (1 1 6)/(3 1 2) planes of the tetragonal phase or (1 1 1), (2 2 0), and (3 1 1) planes of the zinc blende phase. As the Zn ratio increased, the location of dominant peak was slightly moved to higher angle indicating that the crystalline phase became closed to bulk zinc blende. The ionic radius of Zn2+ (0.88nm) is smaller than that of Cu+ (0.91nm) or In3+ (0.94nm), thus, the substitution of Zn2+ for Cu+ or In3+ led to lattice contraction, and the lattice constant of the a-axis decreased from 0.5534, 0.5530, 0.5476, and 0.5457 to 0.5372nm with increasing Zn content. In addition, the particle sizes calculated based on the Scherrer formula were less than 3nm regardless of the Cu:Zn ratio.

Figure 2
Fig. 2 HR-TEM image of ZCIS NCs with different Cu( = In):Zn ratios. (a) 0.2, (b) 0.6, and (c) 1.0. (insets: size distribution of ZCIS NCs from DLS)
shows the HR-TEM (Tecnai G2 F30) image of ZCIS NCs. The prepared NCs were nearly spherical in shape, and the diameter of Cu/Zn = 0.2, 0.6, and 1.0 of ZCIS NC were 3.69, 3.56, and 3.82nm, respectively, measured from dynamic light scattering (DLS). The Cu( = In):Zn ratio had no significant effect on particles size, and their size was closed to XRD results.

Raman scattering is a nondestructive method to identify crystalline phases. In general, CuInS2 can appear in two different crystalline phases, chalcopyrite (CH) and Cu-Au like (CA) ordering. According to Riedle [19

19. T. Riedel, “Raman spectroscopy for the analysis of thin CuInS2 films” (Ph. D. thesis, Technical University of Berlin, 2002).

] and Alvarez-Garcia [20

20. J. Garcia, Characterisation of CuInS2 films for solar cell applications by raman spectroscopy (Ph. D. thesis, University of Barcelona, 2002).

], A1 mode peaks of CH and CA ordering are observed at 293 and 305cm−1, respectively. As shown in Fig. 3
Fig. 3 Raman scattering of ZCIS nanocrystals with different Cu( = In):Zn ratios.
, broad peaks were located at 290-310cm−1 suggesting that the obtained ZCIS NCs comprised a mixture of CH and CA ordering. The other peaks that were observed at around 264 (E3LO, B22LO), 326 (E1TO, B21TO), and 342cm−1(E1LO) were assigned to the CH ordering [21

21. D. Lee and J. Kim, “Characterization of sprayed CuInS2 films by XRD and raman spectroscopy measurements,” Thin Solid Films 518(22), 6537–6541 (2010). [CrossRef]

], and the peak at 478cm−1, observed in the Cu/Zn = 0.8 and 1.0, originated from the Cu2-xS impurity phase [19

19. T. Riedel, “Raman spectroscopy for the analysis of thin CuInS2 films” (Ph. D. thesis, Technical University of Berlin, 2002).

]. Increasing the concentration of Zn led to weakening of the broad A1 peak at around 300cm−1, and the strong peak was observed at about 353cm−1 characteristic of the ZnS structure [22

22. Y. Yu, M. Hyun, S. Nam, D. Lee, B. O, K.-S. Lee, P. Y. Yu, and Y. D. Choi, “Resonant Raman scattering measurements of strains in ZnS epilayers grown on GaP,” J. Appl. Phys. 91(11), 9429–9431 (2002). [CrossRef]

]. These raman spectroscopy results were consistent with the XRD results.

A white LED was fabricated by combining a 460nm InGaN LED chip with ZCIS NCs. Either single 567nm yellow emitting or dual integration of 567nm and 617nm yellow/red emitting ZCIS NCs was employed in wavelength convertor. Figures 5(a)
Fig. 5 Emission spectra of fabricated white LED using an integrating sphere. (a) 460nm InGaN LED pumped with single yellow ZnCuInS nanocrystals, and (b) dual yellow/red ZnCuInS nanocrystals.
, and 5(b) showed the emission spectra (Lab sphere) of the ZCIS NCs based white LED. The single yellow ZCIS NCs based white LED had CIE-1931 chromaticity coordinates of (0.3195, 0.3642), and correlated color temperature of Tc = 6011.7K at 20mA. As a result of the broad FWHM of the ZCIS NCs, the CRI was higher than that of CdSe NCs based white LED. The CRI of the single yellow ZCIS NCs phosphor white LED was 66.5, compared to values of 14.6 and 15.3 reported by Demir et al. [7

7. S. Nizamoglu, T. Ozel, E. Sari, and H. Demir, “White light generation using CdSe/ZnS core–shell nanocrystals hybridized with InGaN/GaN light emitting diodes,” Nanotechnology 18(6), 065709 (2007). [CrossRef]

, 8

8. S. Nizamoglu, G. Zengin, and H. Demir, “Color-converting combinations of nanocrystal emitters for warm-white light generation with high color rendering index,” Appl. Phys. Lett. 92(3), 031102 (2008). [CrossRef]

] and Cho et al. [9

9. H. Wang, K. S. Lee, J. H. Ryu, C. H. Hong, and Y. H. Cho, “White light emitting diodes realized by using an active packaging method with CdSe/ZnS quantum dots dispersed in photosensitive epoxy resins,” Nanotechnology 19(14), 145202 (2008). [CrossRef] [PubMed]

], respectively, using a single yellow CdSe NCs color convertor white LED. The warm and high CRI of white LED was developed using combination of a 460nm blue LED and yellow/red dual emitting ZCIS NCs. The addition of 617nm emitting ZCIS NCs enhanced the red spectral deficiency, thus, the strong red component of R9 was largely increased, and special CRI reached to 84.1. In the case of CdSe NCs based white LED, more than 4 different NCs emission wavelength were required for generating a CRI of white light above 70, which impacted negatively on the overall efficiency due to reabsorption within the NCs. The color temperature was 4256.2K in warm white region, and acceptable color stability was observed with various applied currents. The CIE-1931 chromaticity coordinates were changed from (0.3626, 0.3378) at 20mA to (0.3480, 0.3206) at 50mA. Although the luminous efficacy of 7.8 lm/W was still low, the color properties such as the CRI and color temperature were comparable to those of commercial white LED. Furthermore, the nontoxic, Cd-free nature of the ZCIS NCs makes them promising alternatives to Cd-containing NCs for application in opto-electronic devices.

4. Conclusion

Color tunable strongly luminescent Cd-free ZCIS NCs were successfully synthesized via a facile route. Variation of the Cu/Zn molar ratio in the range 0.2–1.0 induced incremental shifts in the emission wavelength in the range 546–637 nm, with a large stoke shift and broad FWHM of approximately 90 nm. The incorporation of Zn improved the quantum yield significantly to 45.1%, without shell formation. The crystal structure of ZCIS NCs was close to zinc blende, and the lattice constant was decreased with increasing Zn ratio. Furthermore, excellent quality of white LED with CRI of 84.1, and warm color temperature of 4256.2K was achieved by employing dual 560/620nm emitting ZCIS NCs. These results suggest that the Cd-free ZCIS NCs developed in this study hold promise for application to solid-state lighting as viable alternatives to toxic Cd-based NCs.

Acknowledgment

This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology (2012R1A1A2007908). This work was supported by the Human Resources Development the Korea Institute of Energy Technology Evaluation and Planning (20114010203050) grant funded by the Korean government Ministry of Knowledge Economy.

References and links

1.

V. Colvin, M. Schlamp, and A. Alivisatos, “Light-emitting diodes made from cadmium selenide nanocrystals and a semiconducting polymer,” Nature 370(6488), 354–357 (1994). [CrossRef]

2.

Y. Zhang, C. Xie, H. Su, J. Liu, S. Pickering, Y. Wang, W. W. Yu, J. Wang, Y. Wang, J. I. Hahm, N. Dellas, S. E. Mohney, and J. Xu, “Employing heavy metal-free colloidal quantum dots in solution-processed white light-emitting diodes,” Nano Lett. 11(2), 329–332 (2011). [CrossRef] [PubMed]

3.

Q. Guo, S. J. Kim, M. Kar, W. N. Shafarman, R. W. Birkmire, E. A. Stach, R. Agrawal, and H. W. Hillhouse, “Development of CuInSe2 nanocrystal and nanoring inks for low-cost solar cells,” Nano Lett. 8(9), 2982–2987 (2008). [CrossRef] [PubMed]

4.

W. C. Chan and S. Nie, “Quantum dot bioconjugates for ultrasensitive nonisotopic detection,” Science 281(5385), 2016–2018 (1998). [CrossRef] [PubMed]

5.

M. Achermann, M. A. Petruska, S. Kos, D. L. Smith, D. D. Koleske, and V. I. Klimov, “Energy-transfer pumping of semiconductor nanocrystals using an epitaxial quantum well,” Nature 429(6992), 642–646 (2004). [CrossRef] [PubMed]

6.

H. Chen, C. Hsu, and H. Hong, “InGaN–CdSe–ZnSe quantum dots white LEDs,” IEEE Photon. Technol. Lett. 18(1), 193–195 (2006). [CrossRef]

7.

S. Nizamoglu, T. Ozel, E. Sari, and H. Demir, “White light generation using CdSe/ZnS core–shell nanocrystals hybridized with InGaN/GaN light emitting diodes,” Nanotechnology 18(6), 065709 (2007). [CrossRef]

8.

S. Nizamoglu, G. Zengin, and H. Demir, “Color-converting combinations of nanocrystal emitters for warm-white light generation with high color rendering index,” Appl. Phys. Lett. 92(3), 031102 (2008). [CrossRef]

9.

H. Wang, K. S. Lee, J. H. Ryu, C. H. Hong, and Y. H. Cho, “White light emitting diodes realized by using an active packaging method with CdSe/ZnS quantum dots dispersed in photosensitive epoxy resins,” Nanotechnology 19(14), 145202 (2008). [CrossRef] [PubMed]

10.

E. Jang, S. Jun, H. Jang, J. Lim, B. Kim, and Y. Kim, “White-light-emitting diodes with quantum dot color converters for display backlight,” Adv. Mater. (Deerfield Beach Fla.) 22(28), 3076–3080 (2010). [CrossRef]

11.

S. Castro, S. Bailey, R. Raffaelle, K. Banger, and A. Hepp, “Synthesis and characterization of colloidal CuInS2 nanoparticles from a molecular single-source precursor,” J. Phys. Chem. B 108(33), 12429–12435 (2004). [CrossRef]

12.

L. Li, T. Daou, I. Texier, T. Chi, N. Liem, and P. Reiss, “Highly luminescent CuInS2/ZnS core/shell nanocrystals:cadmium-free quantum dots for in vivo imaging,” Chem. Mater. 21(12), 2422–2429 (2009). [CrossRef]

13.

M. Uehara, K. Watanabe, Y. Tajiri, H. Nakamura, and H. Maeda, “Synthesis of CuInS2 fluorescent nanocrystals and enhancement of fluorescence by controlling crystal defect,” J. Chem. Phys. 129(13), 134709 (2008). [CrossRef] [PubMed]

14.

H. Nakamura, W. Kato, M. Uehara, K. Nose, T. Omata, S. Matsuo, M. Miyazaki, and H. Maeda, “Tunable photoluminescence wavelength of chalcopyrite CuInS2-based semiconductor nanocrystals synthesized in a colloidal system,” Chem. Mater. 18(14), 3330–3335 (2006). [CrossRef]

15.

J. Zhang, R. Xie, and W. Yang, “A simple route for highly luminescent quaternary Cu-Zn-In-S nanocrystal emitter,” Chem. Mater. 23(14), 3357–3361 (2011). [CrossRef]

16.

J. Feng, M. Sun, F. Yang, and X. Yang, “A facile approach to synthesize high-quality ZnxCuyInS1.5+x+0.5y nanocrystal emitters,” Chem. Commun. (Camb.) 47(22), 6422–6424 (2011). [CrossRef] [PubMed]

17.

H. Kim, B. Kwon, M. Suh, D. Kang, Y. Kim, and D. Jeon, “Degradation characteristics of red light-emitting CuInS2/ZnS quantum dots as a wavelength converter for LEDs,” Electrochem. Solid-State Lett. 14(10), K55–K57 (2011). [CrossRef]

18.

W. Chung, H. Jung, C. Lee, S. Park, J. Kim, and S. Kim, “Synthesis and application of non-toxic ZnCuInS2/ZnS nanocrystals for white LED by hybridization with conjugated polymer,” J. Electrochem. Soc. 158(12), H1218–H1220 (2011). [CrossRef]

19.

T. Riedel, “Raman spectroscopy for the analysis of thin CuInS2 films” (Ph. D. thesis, Technical University of Berlin, 2002).

20.

J. Garcia, Characterisation of CuInS2 films for solar cell applications by raman spectroscopy (Ph. D. thesis, University of Barcelona, 2002).

21.

D. Lee and J. Kim, “Characterization of sprayed CuInS2 films by XRD and raman spectroscopy measurements,” Thin Solid Films 518(22), 6537–6541 (2010). [CrossRef]

22.

Y. Yu, M. Hyun, S. Nam, D. Lee, B. O, K.-S. Lee, P. Y. Yu, and Y. D. Choi, “Resonant Raman scattering measurements of strains in ZnS epilayers grown on GaP,” J. Appl. Phys. 91(11), 9429–9431 (2002). [CrossRef]

OCIS Codes
(230.3670) Optical devices : Light-emitting diodes
(160.4236) Materials : Nanomaterials
(230.7405) Optical devices : Wavelength conversion devices

ToC Category:
Optical Devices

History
Original Manuscript: July 12, 2012
Revised Manuscript: September 19, 2012
Manuscript Accepted: October 9, 2012
Published: October 18, 2012

Citation
Wonkeun Chung, Hyunchul Jung, Chang Hun Lee, and Sung Hyun Kim, "Fabrication of high color rendering index white LED using Cd-free wavelength tunable Zn doped CuInS2 nanocrystals," Opt. Express 20, 25071-25076 (2012)
http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-20-22-25071


Sort:  Author  |  Year  |  Journal  |  Reset  

References

  1. V. Colvin, M. Schlamp, and A. Alivisatos, “Light-emitting diodes made from cadmium selenide nanocrystals and a semiconducting polymer,” Nature370(6488), 354–357 (1994). [CrossRef]
  2. Y. Zhang, C. Xie, H. Su, J. Liu, S. Pickering, Y. Wang, W. W. Yu, J. Wang, Y. Wang, J. I. Hahm, N. Dellas, S. E. Mohney, and J. Xu, “Employing heavy metal-free colloidal quantum dots in solution-processed white light-emitting diodes,” Nano Lett.11(2), 329–332 (2011). [CrossRef] [PubMed]
  3. Q. Guo, S. J. Kim, M. Kar, W. N. Shafarman, R. W. Birkmire, E. A. Stach, R. Agrawal, and H. W. Hillhouse, “Development of CuInSe2 nanocrystal and nanoring inks for low-cost solar cells,” Nano Lett.8(9), 2982–2987 (2008). [CrossRef] [PubMed]
  4. W. C. Chan and S. Nie, “Quantum dot bioconjugates for ultrasensitive nonisotopic detection,” Science281(5385), 2016–2018 (1998). [CrossRef] [PubMed]
  5. M. Achermann, M. A. Petruska, S. Kos, D. L. Smith, D. D. Koleske, and V. I. Klimov, “Energy-transfer pumping of semiconductor nanocrystals using an epitaxial quantum well,” Nature429(6992), 642–646 (2004). [CrossRef] [PubMed]
  6. H. Chen, C. Hsu, and H. Hong, “InGaN–CdSe–ZnSe quantum dots white LEDs,” IEEE Photon. Technol. Lett.18(1), 193–195 (2006). [CrossRef]
  7. S. Nizamoglu, T. Ozel, E. Sari, and H. Demir, “White light generation using CdSe/ZnS core–shell nanocrystals hybridized with InGaN/GaN light emitting diodes,” Nanotechnology18(6), 065709 (2007). [CrossRef]
  8. S. Nizamoglu, G. Zengin, and H. Demir, “Color-converting combinations of nanocrystal emitters for warm-white light generation with high color rendering index,” Appl. Phys. Lett.92(3), 031102 (2008). [CrossRef]
  9. H. Wang, K. S. Lee, J. H. Ryu, C. H. Hong, and Y. H. Cho, “White light emitting diodes realized by using an active packaging method with CdSe/ZnS quantum dots dispersed in photosensitive epoxy resins,” Nanotechnology19(14), 145202 (2008). [CrossRef] [PubMed]
  10. E. Jang, S. Jun, H. Jang, J. Lim, B. Kim, and Y. Kim, “White-light-emitting diodes with quantum dot color converters for display backlight,” Adv. Mater. (Deerfield Beach Fla.)22(28), 3076–3080 (2010). [CrossRef]
  11. S. Castro, S. Bailey, R. Raffaelle, K. Banger, and A. Hepp, “Synthesis and characterization of colloidal CuInS2 nanoparticles from a molecular single-source precursor,” J. Phys. Chem. B108(33), 12429–12435 (2004). [CrossRef]
  12. L. Li, T. Daou, I. Texier, T. Chi, N. Liem, and P. Reiss, “Highly luminescent CuInS2/ZnS core/shell nanocrystals:cadmium-free quantum dots for in vivo imaging,” Chem. Mater.21(12), 2422–2429 (2009). [CrossRef]
  13. M. Uehara, K. Watanabe, Y. Tajiri, H. Nakamura, and H. Maeda, “Synthesis of CuInS2 fluorescent nanocrystals and enhancement of fluorescence by controlling crystal defect,” J. Chem. Phys.129(13), 134709 (2008). [CrossRef] [PubMed]
  14. H. Nakamura, W. Kato, M. Uehara, K. Nose, T. Omata, S. Matsuo, M. Miyazaki, and H. Maeda, “Tunable photoluminescence wavelength of chalcopyrite CuInS2-based semiconductor nanocrystals synthesized in a colloidal system,” Chem. Mater.18(14), 3330–3335 (2006). [CrossRef]
  15. J. Zhang, R. Xie, and W. Yang, “A simple route for highly luminescent quaternary Cu-Zn-In-S nanocrystal emitter,” Chem. Mater.23(14), 3357–3361 (2011). [CrossRef]
  16. J. Feng, M. Sun, F. Yang, and X. Yang, “A facile approach to synthesize high-quality ZnxCuyInS1.5+x+0.5y nanocrystal emitters,” Chem. Commun. (Camb.)47(22), 6422–6424 (2011). [CrossRef] [PubMed]
  17. H. Kim, B. Kwon, M. Suh, D. Kang, Y. Kim, and D. Jeon, “Degradation characteristics of red light-emitting CuInS2/ZnS quantum dots as a wavelength converter for LEDs,” Electrochem. Solid-State Lett.14(10), K55–K57 (2011). [CrossRef]
  18. W. Chung, H. Jung, C. Lee, S. Park, J. Kim, and S. Kim, “Synthesis and application of non-toxic ZnCuInS2/ZnS nanocrystals for white LED by hybridization with conjugated polymer,” J. Electrochem. Soc.158(12), H1218–H1220 (2011). [CrossRef]
  19. T. Riedel, “Raman spectroscopy for the analysis of thin CuInS2 films” (Ph. D. thesis, Technical University of Berlin, 2002).
  20. J. Garcia, Characterisation of CuInS2 films for solar cell applications by raman spectroscopy (Ph. D. thesis, University of Barcelona, 2002).
  21. D. Lee and J. Kim, “Characterization of sprayed CuInS2 films by XRD and raman spectroscopy measurements,” Thin Solid Films518(22), 6537–6541 (2010). [CrossRef]
  22. Y. Yu, M. Hyun, S. Nam, D. Lee, B. O, K.-S. Lee, P. Y. Yu, and Y. D. Choi, “Resonant Raman scattering measurements of strains in ZnS epilayers grown on GaP,” J. Appl. Phys.91(11), 9429–9431 (2002). [CrossRef]

Cited By

Alert me when this paper is cited

OSA is able to provide readers links to articles that cite this paper by participating in CrossRef's Cited-By Linking service. CrossRef includes content from more than 3000 publishers and societies. In addition to listing OSA journal articles that cite this paper, citing articles from other participating publishers will also be listed.

Figures

Fig. 1 Fig. 2 Fig. 3
 
Fig. 4 Fig. 5
 

« Previous Article  |  Next Article »

OSA is a member of CrossRef.

CrossCheck Deposited