TY  - JOUR
AU  - Tomović, Aleksandar
AU  - Jovanović, Vladimir P.
AU  - Djurišić, Ivana
AU  - PEJIĆ, MILAN M.
AU  - Cerovski, Viktor
AU  - BLESIĆ, SUZANA M.
AU  - Žikić, Radomir
PY  - 2015
UR  - http://rimsi.imsi.bg.ac.rs/handle/123456789/1892
AB  - U ovom radu je prikazana studija mehanizma gašenja fotoluminescencije (FL) tankih amorfnih filmova N,N'-bis(3-methylphenyl)-N,N'-bis(phenyl)benzidine (TPD) izloženih UV zračenju u vazduhu. TPD je organski molekul koji se često koristi u izradi organskih svetlećih dioda (OLED). Prilikom izlaganja TPD filmova UV zračenju u vazduhu, dolazi do fotooksidacije TPD molekula, te iz tog razloga fotoluminescencija TPD filmova opada eksponencijalno sa vremenom osvetljavanja filmova, odnosno sa povećanjem koncentracije nečistoća nastalih usled fotooksidacije. Intenzitet fotoluminescencije opadne na polovinu svoje početne vrednosti u slučaju kada je 0.4 % nečistoća prisutno u filmu. U tom slučaju je srednje rastojanje između nečistoća (akceptora) šest puta veće od srednjeg rastojanja između TPD molekula (donora). Direktan dugodometni Forsterov transfer energije je odbačen kao mehanizam gašenja fotoluminescencije jer je spektralno preklapanje emisije donora i apsorpcije akceptora zanemarljivo. Iz ovog razloga je postulirana ekscitonska difuzija u TPD filmovima, analogno nalazima u postojećoj literaturi. Prisustvo produkata oksidacije je potvrđeno uz pomoć infracrvene (IR) spektroskopije. Takodje, izračunat je IR spektar koristeći teoriju funkcionala gustine (DFT) i dobijeno je dobro slaganje sa eksperimentalnim rezultatima.
AB  - The mechanism of photoluminescence (PL) quenching of thin amorphous N,N′-bis(3-methylphenyl)- N,N′-bis(phenyl)benzidine (TPD) films exposed to UV light in air is studied. TPD is small organic molecule widely used in production of organic light emmiting devices (OLEDs). Photoluminescence of TPD films decays exponentially with time of irradiation, i.e. with the increase of concentration of impurities (photo-oxidized TPD molecules) generated by UV irradiation in air. Intensity of PL decreases to half of its original value when the concentration of impurities reaches 0.4%. Average distance between impurities (acceptors) is almost an order of magnitude larger than average distance between host TPD molecules (donors). Direct long range Förster energy transfer is ruled out as the mechanism of PL quenching, as the overlap between donor and acceptor is lacking, and exciton self-diffusion in TPD films is postulated for the mechanism. The presence of oxidation products is confirmed by infrared (IR) spectroscopy. Vibrational spectra of TPD molecule and few other possible products of photo-oxidation of TPD molecule, obtained by density functional theory, are compared to experimental IR spectra.
PB  - Savez inženjera i tehničara Srbije, Beograd
T2  - TEHNIKA
T1  - Mehanizam gašenja fotoluminescencije u tankim filmovima N,N′-bis(3- methylphenyl)-N,N′-bis(phenyl)benzidine osvetljenih UV svetlošću u vazduhu
T1  - MECHANISM OF PHOTOLUMINESCENCE QUENCHING IN THIN FILMS OF N,N′-BIS(3- METHYLPHENYL)-N,N′-BIS(PHENYL)BENZIDINE IRRADIATED BY UV LIGHT IN AIR
EP  - 914
IS  - 6
SP  - 909
VL  - 70
DO  - 10.5937/tehnika1506909T
ER  - 

@article{
author = "Tomović, Aleksandar and Jovanović, Vladimir P. and Djurišić, Ivana and PEJIĆ, MILAN M. and Cerovski, Viktor and BLESIĆ, SUZANA M. and Žikić, Radomir",
year = "2015",
abstract = "U ovom radu je prikazana studija mehanizma gašenja fotoluminescencije (FL) tankih amorfnih filmova N,N'-bis(3-methylphenyl)-N,N'-bis(phenyl)benzidine (TPD) izloženih UV zračenju u vazduhu. TPD je organski molekul koji se često koristi u izradi organskih svetlećih dioda (OLED). Prilikom izlaganja TPD filmova UV zračenju u vazduhu, dolazi do fotooksidacije TPD molekula, te iz tog razloga fotoluminescencija TPD filmova opada eksponencijalno sa vremenom osvetljavanja filmova, odnosno sa povećanjem koncentracije nečistoća nastalih usled fotooksidacije. Intenzitet fotoluminescencije opadne na polovinu svoje početne vrednosti u slučaju kada je 0.4 % nečistoća prisutno u filmu. U tom slučaju je srednje rastojanje između nečistoća (akceptora) šest puta veće od srednjeg rastojanja između TPD molekula (donora). Direktan dugodometni Forsterov transfer energije je odbačen kao mehanizam gašenja fotoluminescencije jer je spektralno preklapanje emisije donora i apsorpcije akceptora zanemarljivo. Iz ovog razloga je postulirana ekscitonska difuzija u TPD filmovima, analogno nalazima u postojećoj literaturi. Prisustvo produkata oksidacije je potvrđeno uz pomoć infracrvene (IR) spektroskopije. Takodje, izračunat je IR spektar koristeći teoriju funkcionala gustine (DFT) i dobijeno je dobro slaganje sa eksperimentalnim rezultatima., The mechanism of photoluminescence (PL) quenching of thin amorphous N,N′-bis(3-methylphenyl)- N,N′-bis(phenyl)benzidine (TPD) films exposed to UV light in air is studied. TPD is small organic molecule widely used in production of organic light emmiting devices (OLEDs). Photoluminescence of TPD films decays exponentially with time of irradiation, i.e. with the increase of concentration of impurities (photo-oxidized TPD molecules) generated by UV irradiation in air. Intensity of PL decreases to half of its original value when the concentration of impurities reaches 0.4%. Average distance between impurities (acceptors) is almost an order of magnitude larger than average distance between host TPD molecules (donors). Direct long range Förster energy transfer is ruled out as the mechanism of PL quenching, as the overlap between donor and acceptor is lacking, and exciton self-diffusion in TPD films is postulated for the mechanism. The presence of oxidation products is confirmed by infrared (IR) spectroscopy. Vibrational spectra of TPD molecule and few other possible products of photo-oxidation of TPD molecule, obtained by density functional theory, are compared to experimental IR spectra.",
publisher = "Savez inženjera i tehničara Srbije, Beograd",
journal = "TEHNIKA",
title = "Mehanizam gašenja fotoluminescencije u tankim filmovima N,N′-bis(3- methylphenyl)-N,N′-bis(phenyl)benzidine osvetljenih UV svetlošću u vazduhu, MECHANISM OF PHOTOLUMINESCENCE QUENCHING IN THIN FILMS OF N,N′-BIS(3- METHYLPHENYL)-N,N′-BIS(PHENYL)BENZIDINE IRRADIATED BY UV LIGHT IN AIR",
pages = "914-909",
number = "6",
volume = "70",
doi = "10.5937/tehnika1506909T"
}

Tomović, A., Jovanović, V. P., Djurišić, I., PEJIĆ, M. M., Cerovski, V., BLESIĆ, S. M.,& Žikić, R.. (2015). Mehanizam gašenja fotoluminescencije u tankim filmovima N,N′-bis(3- methylphenyl)-N,N′-bis(phenyl)benzidine osvetljenih UV svetlošću u vazduhu. in TEHNIKA
Savez inženjera i tehničara Srbije, Beograd., 70(6), 909-914.
https://doi.org/10.5937/tehnika1506909T

Tomović A, Jovanović VP, Djurišić I, PEJIĆ MM, Cerovski V, BLESIĆ SM, Žikić R. Mehanizam gašenja fotoluminescencije u tankim filmovima N,N′-bis(3- methylphenyl)-N,N′-bis(phenyl)benzidine osvetljenih UV svetlošću u vazduhu. in TEHNIKA. 2015;70(6):909-914.
doi:10.5937/tehnika1506909T .

Tomović, Aleksandar, Jovanović, Vladimir P., Djurišić, Ivana, PEJIĆ, MILAN M., Cerovski, Viktor, BLESIĆ, SUZANA M., Žikić, Radomir, "Mehanizam gašenja fotoluminescencije u tankim filmovima N,N′-bis(3- methylphenyl)-N,N′-bis(phenyl)benzidine osvetljenih UV svetlošću u vazduhu" in TEHNIKA, 70, no. 6 (2015):909-914,
https://doi.org/10.5937/tehnika1506909T . .

TY  - JOUR
AU  - Tomović, Aleksandar
AU  - Jovanović, Vladimir P.
AU  - Djurišić, Ivana
AU  - Cerovski, Viktor
AU  - Nastasijević, Branislav
AU  - Veielović, S. R.
AU  - Radulović, K.
AU  - Žikić, Radomir
PY  - 2015
UR  - http://rimsi.imsi.bg.ac.rs/handle/123456789/876
AB  - The photoluminescence (PL) quenching mechanism of UV light and air-exposed amorphous thin films of 4,4'-bis(2,2-diphenylvinyl)-1,1'-biphenyl (DPVBi), a well-known hole-transport material used in organic light-emitting diodes, is studied. Thin films of DPVBi are stable when exposed to UV light in vacuum but tend to degrade if oxygen is present simultaneously. This is evident from the changes in UV-vis absorption spectra of the latter, showing that degradation rate of DPVBi films is linearly proportional to both oxygen concentration and UV light intensity. Mass spectrometry study of such films revealed a number of different oxygen-containing molecules and fragments of DPVBi thus confirming apparent photo-oxidation process. Also, DFT study of molecular DPVBi with and without oxygen was carried out, the IR spectra calculated for the lowest energy molecules found and the results are compared with the experiment. The most sensitive to photo-oxidation is DPVBi photoluminescence, which decays exponentially with respect to the concentration of photo-oxidized DPVBi molecules (impurities). The PL quantum yield of DPVBi thin film drops to a half of its original value for 0.2% of the impurities present, at which point an average distance between DPVBi molecules (the donors) and photo-oxidized DPVBi species (acceptors) is an order of magnitude larger than the separation between two adjacent molecules. This implies a need for a long-range Forster energy transfer, which we rule out based on the lack of a donor-acceptor spectral overlap. The apparent discrepancy can be removed by postulating exciton self-diffusion in DPVBi thin films, for which there is supporting evidence in existing literature.
PB  - Elsevier, Amsterdam
T2  - Journal of Luminescence
T1  - Fast photoluminescence quenching in thin films of 4,4 '-bis(2,2-diphenylvinyl)-1,1 '-biphenyl exposed to air
EP  - 210
SP  - 204
VL  - 167
DO  - 10.1016/j.jlumin.2015.06.036
ER  - 

@article{
author = "Tomović, Aleksandar and Jovanović, Vladimir P. and Djurišić, Ivana and Cerovski, Viktor and Nastasijević, Branislav and Veielović, S. R. and Radulović, K. and Žikić, Radomir",
year = "2015",
abstract = "The photoluminescence (PL) quenching mechanism of UV light and air-exposed amorphous thin films of 4,4'-bis(2,2-diphenylvinyl)-1,1'-biphenyl (DPVBi), a well-known hole-transport material used in organic light-emitting diodes, is studied. Thin films of DPVBi are stable when exposed to UV light in vacuum but tend to degrade if oxygen is present simultaneously. This is evident from the changes in UV-vis absorption spectra of the latter, showing that degradation rate of DPVBi films is linearly proportional to both oxygen concentration and UV light intensity. Mass spectrometry study of such films revealed a number of different oxygen-containing molecules and fragments of DPVBi thus confirming apparent photo-oxidation process. Also, DFT study of molecular DPVBi with and without oxygen was carried out, the IR spectra calculated for the lowest energy molecules found and the results are compared with the experiment. The most sensitive to photo-oxidation is DPVBi photoluminescence, which decays exponentially with respect to the concentration of photo-oxidized DPVBi molecules (impurities). The PL quantum yield of DPVBi thin film drops to a half of its original value for 0.2% of the impurities present, at which point an average distance between DPVBi molecules (the donors) and photo-oxidized DPVBi species (acceptors) is an order of magnitude larger than the separation between two adjacent molecules. This implies a need for a long-range Forster energy transfer, which we rule out based on the lack of a donor-acceptor spectral overlap. The apparent discrepancy can be removed by postulating exciton self-diffusion in DPVBi thin films, for which there is supporting evidence in existing literature.",
publisher = "Elsevier, Amsterdam",
journal = "Journal of Luminescence",
title = "Fast photoluminescence quenching in thin films of 4,4 '-bis(2,2-diphenylvinyl)-1,1 '-biphenyl exposed to air",
pages = "210-204",
volume = "167",
doi = "10.1016/j.jlumin.2015.06.036"
}

Tomović, A., Jovanović, V. P., Djurišić, I., Cerovski, V., Nastasijević, B., Veielović, S. R., Radulović, K.,& Žikić, R.. (2015). Fast photoluminescence quenching in thin films of 4,4 '-bis(2,2-diphenylvinyl)-1,1 '-biphenyl exposed to air. in Journal of Luminescence
Elsevier, Amsterdam., 167, 204-210.
https://doi.org/10.1016/j.jlumin.2015.06.036

Tomović A, Jovanović VP, Djurišić I, Cerovski V, Nastasijević B, Veielović SR, Radulović K, Žikić R. Fast photoluminescence quenching in thin films of 4,4 '-bis(2,2-diphenylvinyl)-1,1 '-biphenyl exposed to air. in Journal of Luminescence. 2015;167:204-210.
doi:10.1016/j.jlumin.2015.06.036 .

Tomović, Aleksandar, Jovanović, Vladimir P., Djurišić, Ivana, Cerovski, Viktor, Nastasijević, Branislav, Veielović, S. R., Radulović, K., Žikić, Radomir, "Fast photoluminescence quenching in thin films of 4,4 '-bis(2,2-diphenylvinyl)-1,1 '-biphenyl exposed to air" in Journal of Luminescence, 167 (2015):204-210,
https://doi.org/10.1016/j.jlumin.2015.06.036 . .

TY  - JOUR
AU  - Tomović, Aleksandar
AU  - Jovanović, Vladimir P.
AU  - Djurišić, Ivana
AU  - Cerovski, Viktor
AU  - Nastasijević, Branislav
AU  - Veličković, Suzana
AU  - Radulović, Katarina
AU  - Žikić, Radomir
AU  - Srdanov, Vojislav I.
PY  - 2014
UR  - http://rimsi.imsi.bg.ac.rs/handle/123456789/1902
AB  - We studied degradation of 4,4′-bis(2,2′diphenyl vinyl)-1,1′-biphenyl (DPVBi), well know OLED material. Thermally evaporated thin films of DPVBi were irradiated with UV light in ambient, vacuum and under different oxygen pressures. The cause of degradation is reaction between UV excited DPVBi molecules and oxygen, via formation of singlet oxygen or electron transfer from excited DPVBi to molecular oxygen. Reaction rates depend on oxygen concentration and UV light intensity. These reactions lead to formation of oxidized species as evidenced by ASAP and MALDI-TOF mass spectroscopy. Photoluminescence quenching has two parts. One part is reversible and may imply formation of charge transfer complexes and the other is irreversible, caused by formation of oxidized species. IR and absorption spectra are studied by Density Functional Theory and results compared with the experiment.
PB  - Materials Research Society of Serbia
T2  - THE SIXTEENTH ANNUAL CONFERENCE YUCOMAT 2014 Programme and The Book of Abstracts
T1  - Degradation of thin 4,4′-bis(2,2′diphenyl vinyl)-1,1′-biphenyl films by UV light
SP  - 100
UR  - https://hdl.handle.net/21.15107/rcub_rimsi_1902
ER  - 

@article{
author = "Tomović, Aleksandar and Jovanović, Vladimir P. and Djurišić, Ivana and Cerovski, Viktor and Nastasijević, Branislav and Veličković, Suzana and Radulović, Katarina and Žikić, Radomir and Srdanov, Vojislav I.",
year = "2014",
abstract = "We studied degradation of 4,4′-bis(2,2′diphenyl vinyl)-1,1′-biphenyl (DPVBi), well know OLED material. Thermally evaporated thin films of DPVBi were irradiated with UV light in ambient, vacuum and under different oxygen pressures. The cause of degradation is reaction between UV excited DPVBi molecules and oxygen, via formation of singlet oxygen or electron transfer from excited DPVBi to molecular oxygen. Reaction rates depend on oxygen concentration and UV light intensity. These reactions lead to formation of oxidized species as evidenced by ASAP and MALDI-TOF mass spectroscopy. Photoluminescence quenching has two parts. One part is reversible and may imply formation of charge transfer complexes and the other is irreversible, caused by formation of oxidized species. IR and absorption spectra are studied by Density Functional Theory and results compared with the experiment.",
publisher = "Materials Research Society of Serbia",
journal = "THE SIXTEENTH ANNUAL CONFERENCE YUCOMAT 2014 Programme and The Book of Abstracts",
title = "Degradation of thin 4,4′-bis(2,2′diphenyl vinyl)-1,1′-biphenyl films by UV light",
pages = "100",
url = "https://hdl.handle.net/21.15107/rcub_rimsi_1902"
}

Tomović, A., Jovanović, V. P., Djurišić, I., Cerovski, V., Nastasijević, B., Veličković, S., Radulović, K., Žikić, R.,& Srdanov, V. I.. (2014). Degradation of thin 4,4′-bis(2,2′diphenyl vinyl)-1,1′-biphenyl films by UV light. in THE SIXTEENTH ANNUAL CONFERENCE YUCOMAT 2014 Programme and The Book of Abstracts
Materials Research Society of Serbia., 100.
https://hdl.handle.net/21.15107/rcub_rimsi_1902

Tomović A, Jovanović VP, Djurišić I, Cerovski V, Nastasijević B, Veličković S, Radulović K, Žikić R, Srdanov VI. Degradation of thin 4,4′-bis(2,2′diphenyl vinyl)-1,1′-biphenyl films by UV light. in THE SIXTEENTH ANNUAL CONFERENCE YUCOMAT 2014 Programme and The Book of Abstracts. 2014;:100.
https://hdl.handle.net/21.15107/rcub_rimsi_1902 .

Tomović, Aleksandar, Jovanović, Vladimir P., Djurišić, Ivana, Cerovski, Viktor, Nastasijević, Branislav, Veličković, Suzana, Radulović, Katarina, Žikić, Radomir, Srdanov, Vojislav I., "Degradation of thin 4,4′-bis(2,2′diphenyl vinyl)-1,1′-biphenyl films by UV light" in THE SIXTEENTH ANNUAL CONFERENCE YUCOMAT 2014 Programme and The Book of Abstracts (2014):100,
https://hdl.handle.net/21.15107/rcub_rimsi_1902 .