Supporting information for Origin of mechanoluminescence from Cu ...
Supporting information for
Origin of mechanoluminescence from Cu doped ZnS particles embedded in an elastomer film and its application in flexible electro-mechanoluminescent lighting devices Seung Wook Shina, Jeung Pyo Ohb,c, Chang Woo Hongd, Eun Mi Kimb, Jeong Ju Wooc, Gi-Seok Heob,*, and Jin Hyeok Kimd,** a
Department of Chemical Engineering and Materials Science, University of Minnesota, 421 Washington Ave. SE, Minneapolis, Minnesota 55455, USA
b
National Center for Nanoprocess and Equipment, Korea Institute of Industrial Technology, 208-6, Cheomdangwagi-ro, Buk-gu, Gwang-ju, 500-480, Republic of Korea c
d
Department of Physics, Chonnam National University, 77 Yongbong-ro, Buk-gu, Gwang-ju, 500-757, Republic of Korea
Optoelectronic Convergence Research Center, Department of Materials Science and Engineering Chonnam National University, 300 Yongbong-Dong, Puk-Gu, Gwangju 500-757, South Korea
* Corresponding author: (Gi-Seok Heo)
Email:[email protected] TEL: +82-62-6006-171 ** Corresponding author: (Jin Hyeok Kim) Email: [email protected] TEL: +82-62-530-1709
S-1
Experimental Section Materials The Cu doped ZnS particle was purchased and used as received from Osram Sylvania Inc. (GGS 42) without any treatments. The polydimethylsiloxane (PDMS) were purchased from Wacker ELASTOSIL RT601.
Preparation of ML composite films The mechanoluminescence (ML) composite films were prepared by two steps processes. First, the ML composite films were prepared on glass substrates by spin coating technique using mixture with weight ratio of 3:7 between ZnS:Cu particles and PDMS. The curing agent added in the mixture of Cu doped ZnS particles with a weight ratio of 9:1 in an air atmosphere. The spin coating conditions were 100 rpm and 60 seconds at room temperature. The thickness of mixture of PDMS and ZnS:Cu particles prepared by spin coated composite film was approximately 900 μm. Second, the spin coated ML composite films were kept in Bell-jar desiccator for 15 min. due to remove the trapped air bubbles in the ML composite films and then they were cured at 70 °C for 30 min.
Fabrication of flexible electro-mechanoluminescence lighting device The flexible electro-mechanoluminescence (EML) lighting device was fabricated with a multi-layered structure of PDMS/ZITO/mixture of PDMS and ZnS:Cu particles/ZITO/PDMS. (i) The PDMS and PDMS+ ZnS powder layers were prepared on the same process as the preparation of ML composite films. The PDMS film was prepared on glass substrate. After curing process, the glass was unhooked from PDMS layer. (ii) The 600 S-2
nm thick Zinc Indium Tin Oxide (ZITO) thin film, which acts a transparent conducting oxide (TCO) layer and has a low resistivity of 1.66 X 10-3 Ωcm, was prepared by co-sputtering technique using Sn (10 wt) doped In2O3 (99.99 %) and ZnO (99.99 %) targets at room temperature. The detailed preparation of process is described in the refs. [1-3]. (iii) The ML composite film with 50 μm thick, which is mixture of PDMS and ZnS:Cu particles, was prepared on ZITO using spin coating process at 2000 rpm for 60 seconds. (iv) The 600 nm thick ZITO thin film was prepared on ML composite film by sputtering technique and then the
PDMS
film
was
prepared
on
ZITO.
(v)
Finally,
the
PDMS/ZITO/ML
particles/ZITO/PDMS multi-layered structure was pressed at 490 kPa for 5 min. and then it was annealed at 70 °C for 30 min.
Characterizations Stretching-Releasing (S-R) measurement system The optical properties of ML composite films were characterized by StretchingReleasing (S-R) measurement system which is periodically applied the stress with harmonic oscillations to the ML composite films. The ML composite films applied the mechanical stress with uniaxial directions. The distances for stretching and releasing in the S-R measurement system were 3.5 cm and 2 cm. The ML composite film with 3 cm used the S-R measurements. S-R measurement system is well described in the ref. [4] Optical characterization The ML, EL spectra, brightness, and CIE coordinates of the ML composite films were conducted using UV-VIS concave grating spectrometer (Black-Comet, Stellar Net Inc., Florida, USA) ranging from 190 nm to 850 nm at room temperature, which is vertically
S-3
aligned with the ML composite films. The optical resolution is less 1 nm under 25 μm slit. The detector type is 2048 pixel CCD. X-ray diffraction, photoluminescence, and FE-SEM analyses The structural properties of ML composite films were characterized by performing high-resolution X-ray diffraction (XRD, X’pert PRO, Philips, Eindhoven, Netherlands) using a source operated at 40 kV and 100 mA. The cross sectional microstructure of the ML composite films was characterized by using field emission scanning electron microscopy (FE-SEM, Model: JSM-6701F, Japan). XRF The presence of elements and chemical composition for ML composite films were determined by X-ray fluorescence spectroscopy (Rigaku, EDXL-300) without any pretreatment process. The power of X-ray tube excitation was kept at 40 keV and X-ray detector was silicon drift detector. PL The room temperature photoluminescence (PL) of the ZnS based powder was characterized using (APD, SH-4, USA) at Korea Basic Science Institute (KBSI). The excitation source was an Ar ion laser operating at the wavelength of 514 nm. TEM The TEM sample for the ZnS:Cu particles was made by polishing using sandwich structure including Si/ SiO2/mixture of ZnS:Cu particles and epoxy/SiO2/Si on Cu grid with circle shape. The bright-field (BF) transmission electron microscopy (TEM) images and S-4
selective area electron diffraction (SAED) patterns of the ZnS:Cu composite were obtained using JEOL-3010 at an operating voltage of 300 kV. Energy-dispersive X-ray spectra were acquired by energy-dispersive X-ray spectroscopy (EDS).
S-5
Intensity (arb.unit)
(a) Zn S Zn
Cu O
Cu Al
0
2
Mn
4
Zn Cu
Mn
6
8
10
Intensity (arb.unit)
Energy (keV)
(b)
Al
O
Cu
Si
0
2
4
6
8
10
Energy (keV) Figure S1 TEM-EDS spectra of the ZnS:Cu particles obtained from (a) ZnS region and (b) Al region, respectively. References [1] Gi-Seok Heo, Yuji Matsumoto, In-Gi Gim, Hyun-Kee Lee, Jong-Woon Park, Tae-Won Kim, Sol. State Commun. 150 (2010) 223-226 S-6
[2] Gi-Seok Heo, In-Gi Gim, Jong-Woon Park, Kwaang-Yong Kim, Tae-Won Kim, J. Sol. State Chem. 182 (2009) 2937 [3] Gi-Seok Heo, Yuji Matsumoto, In-Gi Gim, Jong-Woon Park, Kwang-Young Kin, TaeWon Kim, Sol. State Commun. 149 (2009) 1731-1734 [4] S. M. Jeong, F. Araoka, Y. Machida, K. Ishikawa, H. Takezoe, S. Nishimura and G. Suzaki, Appl. Phys. Lett., 2008, 92, 083307.
S-7
Origin of mechanoluminescence from Cu doped ZnS particles embedded in an elastomer film and its application in flexible electro-mechanoluminescent lighting devices Seung Wook Shina, Jeung Pyo Ohb,c, Chang Woo Hongd, Eun Mi Kimb, Jeong Ju Wooc, Gi-Seok Heob,*, and Jin Hyeok Kimd,** a
Department of Chemical Engineering and Materials Science, University of Minnesota, 421 Washington Ave. SE, Minneapolis, Minnesota 55455, USA
b
National Center for Nanoprocess and Equipment, Korea Institute of Industrial Technology, 208-6, Cheomdangwagi-ro, Buk-gu, Gwang-ju, 500-480, Republic of Korea c
d
Department of Physics, Chonnam National University, 77 Yongbong-ro, Buk-gu, Gwang-ju, 500-757, Republic of Korea
Optoelectronic Convergence Research Center, Department of Materials Science and Engineering Chonnam National University, 300 Yongbong-Dong, Puk-Gu, Gwangju 500-757, South Korea
* Corresponding author: (Gi-Seok Heo)
Email:[email protected] TEL: +82-62-6006-171 ** Corresponding author: (Jin Hyeok Kim) Email: [email protected] TEL: +82-62-530-1709
S-1
Experimental Section Materials The Cu doped ZnS particle was purchased and used as received from Osram Sylvania Inc. (GGS 42) without any treatments. The polydimethylsiloxane (PDMS) were purchased from Wacker ELASTOSIL RT601.
Preparation of ML composite films The mechanoluminescence (ML) composite films were prepared by two steps processes. First, the ML composite films were prepared on glass substrates by spin coating technique using mixture with weight ratio of 3:7 between ZnS:Cu particles and PDMS. The curing agent added in the mixture of Cu doped ZnS particles with a weight ratio of 9:1 in an air atmosphere. The spin coating conditions were 100 rpm and 60 seconds at room temperature. The thickness of mixture of PDMS and ZnS:Cu particles prepared by spin coated composite film was approximately 900 μm. Second, the spin coated ML composite films were kept in Bell-jar desiccator for 15 min. due to remove the trapped air bubbles in the ML composite films and then they were cured at 70 °C for 30 min.
Fabrication of flexible electro-mechanoluminescence lighting device The flexible electro-mechanoluminescence (EML) lighting device was fabricated with a multi-layered structure of PDMS/ZITO/mixture of PDMS and ZnS:Cu particles/ZITO/PDMS. (i) The PDMS and PDMS+ ZnS powder layers were prepared on the same process as the preparation of ML composite films. The PDMS film was prepared on glass substrate. After curing process, the glass was unhooked from PDMS layer. (ii) The 600 S-2
nm thick Zinc Indium Tin Oxide (ZITO) thin film, which acts a transparent conducting oxide (TCO) layer and has a low resistivity of 1.66 X 10-3 Ωcm, was prepared by co-sputtering technique using Sn (10 wt) doped In2O3 (99.99 %) and ZnO (99.99 %) targets at room temperature. The detailed preparation of process is described in the refs. [1-3]. (iii) The ML composite film with 50 μm thick, which is mixture of PDMS and ZnS:Cu particles, was prepared on ZITO using spin coating process at 2000 rpm for 60 seconds. (iv) The 600 nm thick ZITO thin film was prepared on ML composite film by sputtering technique and then the
PDMS
film
was
prepared
on
ZITO.
(v)
Finally,
the
PDMS/ZITO/ML
particles/ZITO/PDMS multi-layered structure was pressed at 490 kPa for 5 min. and then it was annealed at 70 °C for 30 min.
Characterizations Stretching-Releasing (S-R) measurement system The optical properties of ML composite films were characterized by StretchingReleasing (S-R) measurement system which is periodically applied the stress with harmonic oscillations to the ML composite films. The ML composite films applied the mechanical stress with uniaxial directions. The distances for stretching and releasing in the S-R measurement system were 3.5 cm and 2 cm. The ML composite film with 3 cm used the S-R measurements. S-R measurement system is well described in the ref. [4] Optical characterization The ML, EL spectra, brightness, and CIE coordinates of the ML composite films were conducted using UV-VIS concave grating spectrometer (Black-Comet, Stellar Net Inc., Florida, USA) ranging from 190 nm to 850 nm at room temperature, which is vertically
S-3
aligned with the ML composite films. The optical resolution is less 1 nm under 25 μm slit. The detector type is 2048 pixel CCD. X-ray diffraction, photoluminescence, and FE-SEM analyses The structural properties of ML composite films were characterized by performing high-resolution X-ray diffraction (XRD, X’pert PRO, Philips, Eindhoven, Netherlands) using a source operated at 40 kV and 100 mA. The cross sectional microstructure of the ML composite films was characterized by using field emission scanning electron microscopy (FE-SEM, Model: JSM-6701F, Japan). XRF The presence of elements and chemical composition for ML composite films were determined by X-ray fluorescence spectroscopy (Rigaku, EDXL-300) without any pretreatment process. The power of X-ray tube excitation was kept at 40 keV and X-ray detector was silicon drift detector. PL The room temperature photoluminescence (PL) of the ZnS based powder was characterized using (APD, SH-4, USA) at Korea Basic Science Institute (KBSI). The excitation source was an Ar ion laser operating at the wavelength of 514 nm. TEM The TEM sample for the ZnS:Cu particles was made by polishing using sandwich structure including Si/ SiO2/mixture of ZnS:Cu particles and epoxy/SiO2/Si on Cu grid with circle shape. The bright-field (BF) transmission electron microscopy (TEM) images and S-4
selective area electron diffraction (SAED) patterns of the ZnS:Cu composite were obtained using JEOL-3010 at an operating voltage of 300 kV. Energy-dispersive X-ray spectra were acquired by energy-dispersive X-ray spectroscopy (EDS).
S-5
Intensity (arb.unit)
(a) Zn S Zn
Cu O
Cu Al
0
2
Mn
4
Zn Cu
Mn
6
8
10
Intensity (arb.unit)
Energy (keV)
(b)
Al
O
Cu
Si
0
2
4
6
8
10
Energy (keV) Figure S1 TEM-EDS spectra of the ZnS:Cu particles obtained from (a) ZnS region and (b) Al region, respectively. References [1] Gi-Seok Heo, Yuji Matsumoto, In-Gi Gim, Hyun-Kee Lee, Jong-Woon Park, Tae-Won Kim, Sol. State Commun. 150 (2010) 223-226 S-6
[2] Gi-Seok Heo, In-Gi Gim, Jong-Woon Park, Kwaang-Yong Kim, Tae-Won Kim, J. Sol. State Chem. 182 (2009) 2937 [3] Gi-Seok Heo, Yuji Matsumoto, In-Gi Gim, Jong-Woon Park, Kwang-Young Kin, TaeWon Kim, Sol. State Commun. 149 (2009) 1731-1734 [4] S. M. Jeong, F. Araoka, Y. Machida, K. Ishikawa, H. Takezoe, S. Nishimura and G. Suzaki, Appl. Phys. Lett., 2008, 92, 083307.
S-7
