Serge Beaupré | Université Laval (original) (raw)
Papers by Serge Beaupré
ACS applied materials & interfaces, Jan 30, 2015
The performance of organic photovoltaic devices (OPV) with nanostructured polymer:perylene diimid... more The performance of organic photovoltaic devices (OPV) with nanostructured polymer:perylene diimide (PDI) photoactive layers approaches the levels of the corresponding polymer:fullerene systems. Nevertheless, a coherent understanding of the difficulty for PDI-based OPV devices to deliver high power conversion efficiencies remains elusive. Here we perform a comparative study in a set of four different polymer:PDI OPV model systems. The different device performance observed is attributed to differences in the nanostructural motif of these composites, as determined by wide-angle X-ray scattering (WAXS) measurements. Long range structural order in the PDI domain dictates i) the stabilization energy and ii) the concentration of the PDI excimers in the composites. The quenching of the PDI excimer photoluminescence (PL) is found to be insensitive to the former but it depends on the latter. High PL quenching occurs for low concentration of PDI excimers that are formed in PDI columns with a l...
Macromolecular Theory and Simulations, 2010
ABSTRACT A reliable model that can be used to estimate the electronic properties (i.e., the HOMO,... more ABSTRACT A reliable model that can be used to estimate the electronic properties (i.e., the HOMO, LUMO, and band gap energies) of conjugated polymers would be a great tool for applications in organic electronics such as light-emitting diodes, field-effect transistors, and photovoltaic cells. Recently, poly(2,7-carbazole) derivatives have shown promising results when used as an active donor layer in bulk heterojunction photovoltaic cells with power conversion efficiency exceeding 7%. By using a simple correlation between density functional theory (DFT) theoretical calculations performed on six model compounds (using the repeating unit) and experimental data from the six corresponding polymers, an accurate estimation of the HOMO energy level, the LUMO energy levels, and the band gap of several poly(2,7-carbazole) derivatives was obtained. According to the theoretical data obtained for more than one hundred repeating units, fourteen new copolymers that can be used as p-type materials in bulk heterojunction solar cells were selected and synthesized. Experimental data obtained from these materials were then used to refine the correlation between DFT and experimental data of poly(2,7-carbazole) derivatives.
Chemistry of Materials, 2006
... cells with the following configuration were assembled: ITO-coated glass or plastic/electrochr... more ... cells with the following configuration were assembled: ITO-coated glass or plastic/electrochromic polymer/gel electrolyte/ITO-coated glass or plastic or conducting textile. These copolymers exhibit good optical and electrochemical properties for military camouflage needs with ...
Journal of Physical Chemistry B, 2000
Advanced Energy Materials, 2012
ABSTRACT A water-soluble cationic polythiophene derivative, poly[3-(6-{4-tert-butylpyridiniumyl}-... more ABSTRACT A water-soluble cationic polythiophene derivative, poly[3-(6-{4-tert-butylpyridiniumyl}-hexyl)thiophene-2,5-diyl] [P3(TBP)HT], is combined with anionic poly(3,4-ethylenedioxythiophene):poly(p-styrenesulfonate) (PEDOT:PSS) on indium tin oxide (ITO) substrates via electrostatic layer-by-layer (eLbL) assembly. By varying the number of eLbL layers, the electrode's work function is precisely controlled from 4.6 to 3.8 eV. These polymeric coatings are used as cathodic interfacial modifiers for inverted-mode organic photovoltaics that incorporate a photoactive layer composed of either poly[(3-hexylthiophene)-2,5-diyl] (P3HT) and the fullerene acceptor [6,6-phenyl-C61-butyric acid methyl ester (PC61BM) or the low bandgap polymer [poly({4,8-di(2-ethylhexyloxyl)benzo[1,2-b:4,5-b′]dithiophene}-2,6-diyl)-alt-({5-octylthieno[3,4-c]pyrrole-4,6-dione}-1,3-diyl) (PBDTTPD)] and the electron acceptor [6,6-phenyl-C71-butyric acid methyl ester (PC71BM)]. The power conversion efficiency (PCE) of the resulting photovoltaic device is dependent on the composition of the eLbL-assembled interface and permits the fabrication of devices with efficiencies of 3.8% and 5.6% for P3HT and PBDTTPD donor polymers, respectively. Notably, these devices demonstrate significant stability with a P3HT:PC61BM system maintaining 83% of its original PCE after 1 year of storage and a PBDTTPD:PC71BM system maintaining 97% of its original PCE after over 1000 h of storage in air, according to the ISOS-D-1 shelf protocol.
Synthetic Metals, 2001
We report on the electroluminescent properties of recently synthesized fluorine-based π-conjugate... more We report on the electroluminescent properties of recently synthesized fluorine-based π-conjugated polymers. The spectral emission varies from blue to yellow depending on the composition of the alternated copolymers containing thiophene or phenylene moieties. The luminance of the devices can be enhanced by adequate balancing of the hole and electron injection/transport. Incorporation of a hole transporting molecule in the polymer and
The journal of physical chemistry. B, Jan 30, 2015
Understanding charge separation and charge transport is crucial for improving the efficiency of o... more Understanding charge separation and charge transport is crucial for improving the efficiency of organic solar cells. Their active media are based on organic molecules and polymers, serving as both light-absorbing and transport layers. The charge-transfer (CT) states play an important role, being intermediate for free carrier generation and charge recombination. Here, we use light-induced electron paramagnetic resonance spectroscopy to study the CT dynamics in blends of the polymers P3HT, PCDTBT, and PTB7 with the fullerene derivative C60-PCBM. Time-resolved EPR measurements show strong spin-polarization patterns for all polymer-fullerene blends, confirming predominant generation of singlet CT states and partial orientation ordering near the donor-acceptor interface. These observations allow a comparison with charge separation processes in molecular donor-acceptor systems and in natural and artificial photosynthetic assemblies, and thus the elucidation of the initial steps of sequent...
Synthetic Metals, 2002
In this study, we present spectroscopic and photophysical results on phenylenefluorene oligomers... more In this study, we present spectroscopic and photophysical results on phenylenefluorene oligomers as well as on their corresponding polyesters. To obtain a better correlation, oligomers having ester groups at both ends of the molecules have also been investigated. From ZINDO/S ...
Solar Energy Materials and Solar Cells, 2012
... Tsang a , Jiayun Zhou a , Pierre G. Verly a , Jianping Lu a , Corresponding Author Contact In... more ... Tsang a , Jiayun Zhou a , Pierre G. Verly a , Jianping Lu a , Corresponding Author Contact Information , E-mail The Corresponding Author , Serge Beaupré b , Mario Leclerc b ... Cs 2 CO 3 ) [7], is deposited on the ITO electrode to lower its work function, and a thin layer of MoO x is ...
Organic Electronics, 2011
We investigated the effect of solvents on the morphology, charge transport and device performance... more We investigated the effect of solvents on the morphology, charge transport and device performance of poly[N-9 00 -hepta-decanyl-2,7-carbazole-alt-5,5-(4 0 ,7 0 -di-2-thienyl-2 0 ,1 0 ,3 0benzothiadiazole)] (PCDTBT) and [6,6]-phenyl C71-butyric acid methyl ester (PC 70 BM) based solar cells. To carry out this investigation, chloroform and 1,2-dichlorobenzene were chosen as good solvents of the two compounds. Films prepared with chloroform exhibit larger domains than those prepared with 1,2-dichlorobenzene and their size increases with the amount of PC 70 BM. Fine tuning of the domain size was realized by using a solvent of mixed chloroform and 1,2-dichlorobenzene. At a mixing ratio of 50%:50%, a power conversion efficiency of 6.1% was achieved on PCDTBT:PC 70 BM (1:3) devices with an active area of 1 cm 2 , under air mass 1.5 global (AM 1.5 G) irradiation at 100 mW/cm 2 .
Organic Electronics, 2012
ABSTRACT In this work, two high boiling-point solvents (1-chloronaphthalene (CN) and 1,8-diiodooc... more ABSTRACT In this work, two high boiling-point solvents (1-chloronaphthalene (CN) and 1,8-diiodooctane (DIO)) were utilized as co-additives in ortho-dichlorobenzene (ODCB) and chlorobenzene (CB) solutions to fine tune the donor and acceptor domains in the bulk heterojunction (BHJ) of poly(benzo[1,2-b:4,5-b′]dithiophene-alt-thieno[3,4-c]pyrrole-4,6-dione) (PBDTTPD) and fullerene derivatives. A power conversion efficiency of 7.1% and a fill factor up to 70% were obtained for solar cells with active area of 1 cm2 when using [6,6]-phenyl C61-butyric acid methyl ester (PC60BM) as acceptor, suggesting that an optimized morphology was achieved.
Nature Photonics, 2009
Nature Photonics offers a unique mix of news and reviews alongside top-quality research papers. P... more Nature Photonics offers a unique mix of news and reviews alongside top-quality research papers. Published monthly, in print and online, the journal reflects the entire spectrum of photonics and optics.
Macromolecules, 2000
The thermochromic and solvatochromic properties of a series of fluorene-based conjugated polymers... more The thermochromic and solvatochromic properties of a series of fluorene-based conjugated polymers have been investigated. Both poly(2,7-(9,9-dioctylfluorene)) and poly(2,5-(thiophene)-alt-2,7-(9,9-dioctylfluorene)) have revealed interesting chromic properties which, on the basis of ...
Macromolecules, 2001
... Michel Belletête, Jean-Francois Morin, Serge Beaupré, Maxime Ranger, Mario Leclerc, ... more ... Michel Belletête, Jean-Francois Morin, Serge Beaupré, Maxime Ranger, Mario Leclerc, and Gilles Durocher* . Laboratoire de photophysique moléculaire, Département de Chimie, Université de Montréal, CP 6128, Succ. ...
The Journal of Physical Chemistry Letters, 2012
PBDTTPD is a conjugated polymer with high power conversion efficiency if used in organic solar ce... more PBDTTPD is a conjugated polymer with high power conversion efficiency if used in organic solar cells together with fullerene derivatives. We have investigated for the first time the excited state dynamics of pristine PBDTTPD thin film as well as the ultrafast evolution of charge carriers in PBDTTPD:PCBM bulk heterojunction blend using femtosecond transient absorption spectroscopy. In the latter, charges appear within the time resolution of the experiment (<100 fs), but clean spectral signatures allowed to directly follow slower ∼1 ps charge separation. Only the slower quenching component competes with exciton−exciton and exciton−charge annihilation, leading to a reduced yield of charge carriers at high laser fluence. Our excellent measuring sensitivity made it possible to reduce pump power to a point where annihilation is quasi suppressed. In this case >80% of charges survive after 1 ns; the rest recombines (most probably geminately) on the 200 ps time scale.
Journal of Optics A: Pure and Applied Optics, 2002
... Nicolas Drolet1,2, Serge Beaupré1, Jean-François Morin1, Ye Tao2 and Mario Leclerc1,3 ... 20 ... more ... Nicolas Drolet1,2, Serge Beaupré1, Jean-François Morin1, Ye Tao2 and Mario Leclerc1,3 ... 20 L1942 [12] Ranger M, Rondeau D and Leclerc M 1997 Macromolecules 30 7686 [13] Donat-Bouillud A, Lévesque I, Tao Y, D'Iorio M, Beaupré S, Blondin P, Ranger M, Bouchard J ...
Journal of Materials Chemistry, 2009
We have studied the utilization of PCDTBT, an alternating poly(2,7-carbazole) derivative, in orga... more We have studied the utilization of PCDTBT, an alternating poly(2,7-carbazole) derivative, in organic bulk heterojunction solar cells. The effect of polymer molecular weight, PCDTBT:[60]PCBM ratio, and active layer thickness on the device performance is reported. The best ...
Chemistry of Materials, 2006
... cells with the following configuration were assembled: ITO-coated glass or plastic/electrochr... more ... cells with the following configuration were assembled: ITO-coated glass or plastic/electrochromic polymer/gel electrolyte/ITO-coated glass or plastic or conducting textile. These copolymers exhibit good optical and electrochemical properties for military camouflage needs with ...
Chemical Physics Letters, 2000
The optical and photophysical properties of a terfluorene, isolated and incorporated in a polyest... more The optical and photophysical properties of a terfluorene, isolated and incorporated in a polyester, are reported. A similar oligofluorene having carboxylic acid groups at each end of the molecule has also been studied. This molecule provides a better correlation with its corresponding polyester. The fully relaxed single-bond torsional potentials of both oligofluorenes Ž . were evaluated with the aid of semiempirical calculations AM1 . The incorporation of the terfluorene in the polyester does not change its conformation and spectral properties. On the other hand, the luminescence intensity of the polyester Ž
Applied Physics Letters, 2009
ACS applied materials & interfaces, Jan 30, 2015
The performance of organic photovoltaic devices (OPV) with nanostructured polymer:perylene diimid... more The performance of organic photovoltaic devices (OPV) with nanostructured polymer:perylene diimide (PDI) photoactive layers approaches the levels of the corresponding polymer:fullerene systems. Nevertheless, a coherent understanding of the difficulty for PDI-based OPV devices to deliver high power conversion efficiencies remains elusive. Here we perform a comparative study in a set of four different polymer:PDI OPV model systems. The different device performance observed is attributed to differences in the nanostructural motif of these composites, as determined by wide-angle X-ray scattering (WAXS) measurements. Long range structural order in the PDI domain dictates i) the stabilization energy and ii) the concentration of the PDI excimers in the composites. The quenching of the PDI excimer photoluminescence (PL) is found to be insensitive to the former but it depends on the latter. High PL quenching occurs for low concentration of PDI excimers that are formed in PDI columns with a l...
Macromolecular Theory and Simulations, 2010
ABSTRACT A reliable model that can be used to estimate the electronic properties (i.e., the HOMO,... more ABSTRACT A reliable model that can be used to estimate the electronic properties (i.e., the HOMO, LUMO, and band gap energies) of conjugated polymers would be a great tool for applications in organic electronics such as light-emitting diodes, field-effect transistors, and photovoltaic cells. Recently, poly(2,7-carbazole) derivatives have shown promising results when used as an active donor layer in bulk heterojunction photovoltaic cells with power conversion efficiency exceeding 7%. By using a simple correlation between density functional theory (DFT) theoretical calculations performed on six model compounds (using the repeating unit) and experimental data from the six corresponding polymers, an accurate estimation of the HOMO energy level, the LUMO energy levels, and the band gap of several poly(2,7-carbazole) derivatives was obtained. According to the theoretical data obtained for more than one hundred repeating units, fourteen new copolymers that can be used as p-type materials in bulk heterojunction solar cells were selected and synthesized. Experimental data obtained from these materials were then used to refine the correlation between DFT and experimental data of poly(2,7-carbazole) derivatives.
Chemistry of Materials, 2006
... cells with the following configuration were assembled: ITO-coated glass or plastic/electrochr... more ... cells with the following configuration were assembled: ITO-coated glass or plastic/electrochromic polymer/gel electrolyte/ITO-coated glass or plastic or conducting textile. These copolymers exhibit good optical and electrochemical properties for military camouflage needs with ...
Journal of Physical Chemistry B, 2000
Advanced Energy Materials, 2012
ABSTRACT A water-soluble cationic polythiophene derivative, poly[3-(6-{4-tert-butylpyridiniumyl}-... more ABSTRACT A water-soluble cationic polythiophene derivative, poly[3-(6-{4-tert-butylpyridiniumyl}-hexyl)thiophene-2,5-diyl] [P3(TBP)HT], is combined with anionic poly(3,4-ethylenedioxythiophene):poly(p-styrenesulfonate) (PEDOT:PSS) on indium tin oxide (ITO) substrates via electrostatic layer-by-layer (eLbL) assembly. By varying the number of eLbL layers, the electrode's work function is precisely controlled from 4.6 to 3.8 eV. These polymeric coatings are used as cathodic interfacial modifiers for inverted-mode organic photovoltaics that incorporate a photoactive layer composed of either poly[(3-hexylthiophene)-2,5-diyl] (P3HT) and the fullerene acceptor [6,6-phenyl-C61-butyric acid methyl ester (PC61BM) or the low bandgap polymer [poly({4,8-di(2-ethylhexyloxyl)benzo[1,2-b:4,5-b′]dithiophene}-2,6-diyl)-alt-({5-octylthieno[3,4-c]pyrrole-4,6-dione}-1,3-diyl) (PBDTTPD)] and the electron acceptor [6,6-phenyl-C71-butyric acid methyl ester (PC71BM)]. The power conversion efficiency (PCE) of the resulting photovoltaic device is dependent on the composition of the eLbL-assembled interface and permits the fabrication of devices with efficiencies of 3.8% and 5.6% for P3HT and PBDTTPD donor polymers, respectively. Notably, these devices demonstrate significant stability with a P3HT:PC61BM system maintaining 83% of its original PCE after 1 year of storage and a PBDTTPD:PC71BM system maintaining 97% of its original PCE after over 1000 h of storage in air, according to the ISOS-D-1 shelf protocol.
Synthetic Metals, 2001
We report on the electroluminescent properties of recently synthesized fluorine-based π-conjugate... more We report on the electroluminescent properties of recently synthesized fluorine-based π-conjugated polymers. The spectral emission varies from blue to yellow depending on the composition of the alternated copolymers containing thiophene or phenylene moieties. The luminance of the devices can be enhanced by adequate balancing of the hole and electron injection/transport. Incorporation of a hole transporting molecule in the polymer and
The journal of physical chemistry. B, Jan 30, 2015
Understanding charge separation and charge transport is crucial for improving the efficiency of o... more Understanding charge separation and charge transport is crucial for improving the efficiency of organic solar cells. Their active media are based on organic molecules and polymers, serving as both light-absorbing and transport layers. The charge-transfer (CT) states play an important role, being intermediate for free carrier generation and charge recombination. Here, we use light-induced electron paramagnetic resonance spectroscopy to study the CT dynamics in blends of the polymers P3HT, PCDTBT, and PTB7 with the fullerene derivative C60-PCBM. Time-resolved EPR measurements show strong spin-polarization patterns for all polymer-fullerene blends, confirming predominant generation of singlet CT states and partial orientation ordering near the donor-acceptor interface. These observations allow a comparison with charge separation processes in molecular donor-acceptor systems and in natural and artificial photosynthetic assemblies, and thus the elucidation of the initial steps of sequent...
Synthetic Metals, 2002
In this study, we present spectroscopic and photophysical results on phenylenefluorene oligomers... more In this study, we present spectroscopic and photophysical results on phenylenefluorene oligomers as well as on their corresponding polyesters. To obtain a better correlation, oligomers having ester groups at both ends of the molecules have also been investigated. From ZINDO/S ...
Solar Energy Materials and Solar Cells, 2012
... Tsang a , Jiayun Zhou a , Pierre G. Verly a , Jianping Lu a , Corresponding Author Contact In... more ... Tsang a , Jiayun Zhou a , Pierre G. Verly a , Jianping Lu a , Corresponding Author Contact Information , E-mail The Corresponding Author , Serge Beaupré b , Mario Leclerc b ... Cs 2 CO 3 ) [7], is deposited on the ITO electrode to lower its work function, and a thin layer of MoO x is ...
Organic Electronics, 2011
We investigated the effect of solvents on the morphology, charge transport and device performance... more We investigated the effect of solvents on the morphology, charge transport and device performance of poly[N-9 00 -hepta-decanyl-2,7-carbazole-alt-5,5-(4 0 ,7 0 -di-2-thienyl-2 0 ,1 0 ,3 0benzothiadiazole)] (PCDTBT) and [6,6]-phenyl C71-butyric acid methyl ester (PC 70 BM) based solar cells. To carry out this investigation, chloroform and 1,2-dichlorobenzene were chosen as good solvents of the two compounds. Films prepared with chloroform exhibit larger domains than those prepared with 1,2-dichlorobenzene and their size increases with the amount of PC 70 BM. Fine tuning of the domain size was realized by using a solvent of mixed chloroform and 1,2-dichlorobenzene. At a mixing ratio of 50%:50%, a power conversion efficiency of 6.1% was achieved on PCDTBT:PC 70 BM (1:3) devices with an active area of 1 cm 2 , under air mass 1.5 global (AM 1.5 G) irradiation at 100 mW/cm 2 .
Organic Electronics, 2012
ABSTRACT In this work, two high boiling-point solvents (1-chloronaphthalene (CN) and 1,8-diiodooc... more ABSTRACT In this work, two high boiling-point solvents (1-chloronaphthalene (CN) and 1,8-diiodooctane (DIO)) were utilized as co-additives in ortho-dichlorobenzene (ODCB) and chlorobenzene (CB) solutions to fine tune the donor and acceptor domains in the bulk heterojunction (BHJ) of poly(benzo[1,2-b:4,5-b′]dithiophene-alt-thieno[3,4-c]pyrrole-4,6-dione) (PBDTTPD) and fullerene derivatives. A power conversion efficiency of 7.1% and a fill factor up to 70% were obtained for solar cells with active area of 1 cm2 when using [6,6]-phenyl C61-butyric acid methyl ester (PC60BM) as acceptor, suggesting that an optimized morphology was achieved.
Nature Photonics, 2009
Nature Photonics offers a unique mix of news and reviews alongside top-quality research papers. P... more Nature Photonics offers a unique mix of news and reviews alongside top-quality research papers. Published monthly, in print and online, the journal reflects the entire spectrum of photonics and optics.
Macromolecules, 2000
The thermochromic and solvatochromic properties of a series of fluorene-based conjugated polymers... more The thermochromic and solvatochromic properties of a series of fluorene-based conjugated polymers have been investigated. Both poly(2,7-(9,9-dioctylfluorene)) and poly(2,5-(thiophene)-alt-2,7-(9,9-dioctylfluorene)) have revealed interesting chromic properties which, on the basis of ...
Macromolecules, 2001
... Michel Belletête, Jean-Francois Morin, Serge Beaupré, Maxime Ranger, Mario Leclerc, ... more ... Michel Belletête, Jean-Francois Morin, Serge Beaupré, Maxime Ranger, Mario Leclerc, and Gilles Durocher* . Laboratoire de photophysique moléculaire, Département de Chimie, Université de Montréal, CP 6128, Succ. ...
The Journal of Physical Chemistry Letters, 2012
PBDTTPD is a conjugated polymer with high power conversion efficiency if used in organic solar ce... more PBDTTPD is a conjugated polymer with high power conversion efficiency if used in organic solar cells together with fullerene derivatives. We have investigated for the first time the excited state dynamics of pristine PBDTTPD thin film as well as the ultrafast evolution of charge carriers in PBDTTPD:PCBM bulk heterojunction blend using femtosecond transient absorption spectroscopy. In the latter, charges appear within the time resolution of the experiment (<100 fs), but clean spectral signatures allowed to directly follow slower ∼1 ps charge separation. Only the slower quenching component competes with exciton−exciton and exciton−charge annihilation, leading to a reduced yield of charge carriers at high laser fluence. Our excellent measuring sensitivity made it possible to reduce pump power to a point where annihilation is quasi suppressed. In this case >80% of charges survive after 1 ns; the rest recombines (most probably geminately) on the 200 ps time scale.
Journal of Optics A: Pure and Applied Optics, 2002
... Nicolas Drolet1,2, Serge Beaupré1, Jean-François Morin1, Ye Tao2 and Mario Leclerc1,3 ... 20 ... more ... Nicolas Drolet1,2, Serge Beaupré1, Jean-François Morin1, Ye Tao2 and Mario Leclerc1,3 ... 20 L1942 [12] Ranger M, Rondeau D and Leclerc M 1997 Macromolecules 30 7686 [13] Donat-Bouillud A, Lévesque I, Tao Y, D'Iorio M, Beaupré S, Blondin P, Ranger M, Bouchard J ...
Journal of Materials Chemistry, 2009
We have studied the utilization of PCDTBT, an alternating poly(2,7-carbazole) derivative, in orga... more We have studied the utilization of PCDTBT, an alternating poly(2,7-carbazole) derivative, in organic bulk heterojunction solar cells. The effect of polymer molecular weight, PCDTBT:[60]PCBM ratio, and active layer thickness on the device performance is reported. The best ...
Chemistry of Materials, 2006
... cells with the following configuration were assembled: ITO-coated glass or plastic/electrochr... more ... cells with the following configuration were assembled: ITO-coated glass or plastic/electrochromic polymer/gel electrolyte/ITO-coated glass or plastic or conducting textile. These copolymers exhibit good optical and electrochemical properties for military camouflage needs with ...
Chemical Physics Letters, 2000
The optical and photophysical properties of a terfluorene, isolated and incorporated in a polyest... more The optical and photophysical properties of a terfluorene, isolated and incorporated in a polyester, are reported. A similar oligofluorene having carboxylic acid groups at each end of the molecule has also been studied. This molecule provides a better correlation with its corresponding polyester. The fully relaxed single-bond torsional potentials of both oligofluorenes Ž . were evaluated with the aid of semiempirical calculations AM1 . The incorporation of the terfluorene in the polyester does not change its conformation and spectral properties. On the other hand, the luminescence intensity of the polyester Ž
Applied Physics Letters, 2009