TY  - CHAP
AU  - Tomović, Aleksandar
AU  - Djurišić, Ivana
AU  - Žikić, Radomir
AU  - Pejić, Milan
AU  - Jovanović, Vladimir P.
PY  - 2017
UR  - http://rimsi.imsi.bg.ac.rs/handle/123456789/1898
AB  - There is an ongoing interest in organic materials due to their application in various organic electronic devices. However stability of organic materials limits their potential use. They are prone to degradation both during the working life and storage. One of the main causes is extrinsic degradation, under the influence of oxygen and moisture. This problem can be solved by encapsulation of devices. However no encapsulation is perfect. This paper presents a study of interaction of thin films of well-known organic blue emitters, namely N,N′-bis(3-methylphenyl)-N,N′-bis(phenyl)benzidine (TPD) and 4,4′-bis(2,2-diphenylvinyl)-1,1′-biphenyl (DPVBi), with UV light in air. Films of both materials are stable in vacuum, but readily degrade in the presence of oxygen. Thus, the necessary condition for interaction (degradation) is the simultaneous presence of UV light and oxygen. Chemical analysis of irradiated films by mass and infrared spectroscopy revealed presence of oxidized species (impurities). These impurities are responsible for increased morphological stability of irradiated films and quenching of photoluminescence (PL). Only small amount of impurities, 0.4 % (0.2 %) for TPD (DPVBi), causes 50 % decrease of PL. This implies a non-trivial mechanism of quenching. For both molecules it was found that distance between impurities is smaller or equal to exciton diffusion length, which is the necessary condition for quenching. Following mechanism of quenching is proposed: exciton diffuses by hopping form one host molecule (DPVBi or TPD) to another through Förster resonant energy transfer in a random walk manner. If, during its lifetime, it comes to proximity of an impurity, a PL quenching process occurs. Findings of this study are important because they show that even a small amount of oxygen that penetrates a blue emitter layer would impair luminescence efficiency of a device. Moreover, the absorption of its own radiation would additionally contribute to the rate of degradation of a device. It is reasonable to expect that transport properties would also be affected when materials are used as a hole-transporting layer in OLEDs.
PB  - Atlantis Press, Paris
T2  - Proceedings of the IV Advanced Ceramics and Applications Conference
T1  - Interaction of UV Irradiation with Thin Films of Organic Molecules
EP  - 347
SP  - 317
DO  - 10.2991/978-94-6239-213-7_23
ER  - 

@inbook{
author = "Tomović, Aleksandar and Djurišić, Ivana and Žikić, Radomir and Pejić, Milan and Jovanović, Vladimir P.",
year = "2017",
abstract = "There is an ongoing interest in organic materials due to their application in various organic electronic devices. However stability of organic materials limits their potential use. They are prone to degradation both during the working life and storage. One of the main causes is extrinsic degradation, under the influence of oxygen and moisture. This problem can be solved by encapsulation of devices. However no encapsulation is perfect. This paper presents a study of interaction of thin films of well-known organic blue emitters, namely N,N′-bis(3-methylphenyl)-N,N′-bis(phenyl)benzidine (TPD) and 4,4′-bis(2,2-diphenylvinyl)-1,1′-biphenyl (DPVBi), with UV light in air. Films of both materials are stable in vacuum, but readily degrade in the presence of oxygen. Thus, the necessary condition for interaction (degradation) is the simultaneous presence of UV light and oxygen. Chemical analysis of irradiated films by mass and infrared spectroscopy revealed presence of oxidized species (impurities). These impurities are responsible for increased morphological stability of irradiated films and quenching of photoluminescence (PL). Only small amount of impurities, 0.4 % (0.2 %) for TPD (DPVBi), causes 50 % decrease of PL. This implies a non-trivial mechanism of quenching. For both molecules it was found that distance between impurities is smaller or equal to exciton diffusion length, which is the necessary condition for quenching. Following mechanism of quenching is proposed: exciton diffuses by hopping form one host molecule (DPVBi or TPD) to another through Förster resonant energy transfer in a random walk manner. If, during its lifetime, it comes to proximity of an impurity, a PL quenching process occurs. Findings of this study are important because they show that even a small amount of oxygen that penetrates a blue emitter layer would impair luminescence efficiency of a device. Moreover, the absorption of its own radiation would additionally contribute to the rate of degradation of a device. It is reasonable to expect that transport properties would also be affected when materials are used as a hole-transporting layer in OLEDs.",
publisher = "Atlantis Press, Paris",
journal = "Proceedings of the IV Advanced Ceramics and Applications Conference",
booktitle = "Interaction of UV Irradiation with Thin Films of Organic Molecules",
pages = "347-317",
doi = "10.2991/978-94-6239-213-7_23"
}

Tomović, A., Djurišić, I., Žikić, R., Pejić, M.,& Jovanović, V. P.. (2017). Interaction of UV Irradiation with Thin Films of Organic Molecules. in Proceedings of the IV Advanced Ceramics and Applications Conference
Atlantis Press, Paris., 317-347.
https://doi.org/10.2991/978-94-6239-213-7_23

Tomović A, Djurišić I, Žikić R, Pejić M, Jovanović VP. Interaction of UV Irradiation with Thin Films of Organic Molecules. in Proceedings of the IV Advanced Ceramics and Applications Conference. 2017;:317-347.
doi:10.2991/978-94-6239-213-7_23 .

Tomović, Aleksandar, Djurišić, Ivana, Žikić, Radomir, Pejić, Milan, Jovanović, Vladimir P., "Interaction of UV Irradiation with Thin Films of Organic Molecules" in Proceedings of the IV Advanced Ceramics and Applications Conference (2017):317-347,
https://doi.org/10.2991/978-94-6239-213-7_23 . .

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 . .