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National Institute of Materials Physics – Romania

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Proiect: 78/2011

Director de Proiect: Dr. Silviu Polosan

Tip Proiect: National

Program: IDEI

Finantat de: Unitatea Executiva pentru Finantarea Invatamantului Superior, a Cercetarii, Dezvoltarii si Inovarii (UEFISCDI), PN-II-ID-PCE-2011-3-0620

Contractor: National Institute of Materials Physics

Status: Finalizat

Data de incepere: 1 October, 2011

Data de finalizare: 1 October, 2016

Abstract proiect:

Dispozitivele electroluminescente (OLED) sunt, in mare parte, constituite din straturi subtiri organice, formand o structura multistrat intre doi electrozi: anod si catod. Purtatorii de sarcina injectati dinspre electrozi se deplaseaza in stratul de recombinare/emitator situat in mijlocul structurii, unde electronii si golurile se recombina si excita moleculele de dopant. Structura acestor straturi organice si alegerea electrozilor sunt concepute astfel incat sa maximizeze procesul de recombinare in stratul emisiv, crescand eficienta emisiei de lumina din dispozitivele OLED. Stratul activ consta dintr-un compus organometalic dispersat in polimer conductor. Acest compus organometalic (dopant) este format dintr-un ion de metal greu legat de trei sau mai multi liganzi. Scopul proiectului este obtinerea de dispozitive electroluminescente cu emisia a cel putin doua culori, prin schimbarea liganzilor pe acelasi compus organometalic. De asemenea, este importanta determinarea stabilitatii in timp a acestor dispozitive pentru evitarea ruperii structurilor moleculare.

Identificarea problemelor ce apar si a noutatilor propuse in acest proiect:

a) Imbunatatirea injectiei de la anod, prin acoperirea substratului ITO cu un strat subtire de nanofire de ZnO pentru a asigura o conductie mai buna in dispozitivul OLED.

b) Sinteza si caracterizarea unui compus organometalic cu emisie duala utilizand doua tipuri de liganzi care sa asigure fosforescente diferite.

c) Selectia si sinteza polimerilor conductori transparenti pentru optimizarea purtatorilor de sarcina in dispozitive OLED.

d) Controlul injectiei purtatorilor de sarcina prin inglobarea unor nanoparticulelor magnetice si metalice in structura sandwich, care actioneaza ca si capcane de electroni si goluri.

Obiectivele proiectului:

1. Modelarea teoretica a proceselor de fosforescenta in compusul organometalic cu doua tipuri de liganzi.

2. Obtinerea compusului organometalic pe baza de iridiu cu emisie duala.

3. Dispersia compusului organometalic in matrici polimerice transparente si izolatoare pentru studiul stabilitatii fizice si chimice prin masuratori de spectroscopie optica.

4. Obtinerea stratului emisiv prin dispersia compusului organometalic in polimeri conductori si transparenti.

5. Obtinerea structurilor multistrat prin adaugarea stratului emisiv obtinut prin dispersia compusului organometalic in doua tipuri de polimeri conductori. Masurarea parametrilor de functionare a structurilor multistrat.

6. Controlul injectiei de sarcina in structurile OLED obtinute prin inglobarea de nanoparticule magnetice si metalice cu rol de captura de sarcina.

Echipa:

  1. Polosan Silviu- Dr., CS I
  2. Ciobotaru Iulia Corina - Doctorand, Master Inginerie Chimica
  3. Iovu Horia- Prof. Dr., Cercetator cu experienta
  4. Enculescu Ionut - Dr., CS I
  5. Tudor Elena - tehnician

1. Raport de activitate 2011-2014

2. Raport de activitate 2015

3. Raport de activitate 2016

4. Raport de activitate 2011-2016

 

1. Optimizarea teoretica a moleculei de compus organometalic IrQ(ppy)2 folosind geometria spatiala a compusului Ir(ppy)3 in care un ligand de fenilpiridina este inlocuit cu cel de chinolina.

2. Determinarea starii fundamentale si a starilor excitate a moleculei de IrQ(ppy)2- modelare teoretica utilizand teoria densitatilor functionale dependente de timp. Spectrul teoretic de absorbtie a fost construit utilizand tariile de oscillator ale fiecarei tranzitii.

3. Hibridizarea intre orbitalii 5d ai Ir3+ si orbitalii π ai liganzilor au aratat un puternic character metalic in legaturile iridiu-fenilpiridina (66% si 43%) si un slab character metalic in legatura iridium-chinolina (16.8%). Analiza distributiei de sarcina pe fiecare orbital metalic a aratat o mica delocalizare de sarcina pe chinolina si o puternica delocalizare pe fenilpiridina. Efectele de solvatare induc un fenomen de deplasare a fosforescentelor prin schimbarea matricii polimerice conductoare ca rezultat al interactiei dipolare intermoleculare.

4. Obtinerea in doua etape a compusului organometalic Ir(ppy)2 : a) compusul intermediar [(C^N)2Ir-μ-Cl]2 si b) compusul final IrQ(ppy)2 prin adaugarea de 8-chinolol la compusul intermediar.5. Analize spectroscopice ale pulberii de IrQ(ppy)2 dizolvate in diversi solventi (chloroform, etanol). Recristalizarea Ir(ppy)2 din cloroform. Caracterizari structural ale pulberii cristaline de IrQ(ppy)2 (XRD, DSC, TGA, XPS, SEM, CL, FT-IR  si Raman).

6. Dispersia pulberii de IrQ(ppy)2 in PMMA si polistiren. Analize spectroscopice si structurale (FT-IR, Raman, DSC, TGA, SEM, CL, XPS).

7. Depunerea electrochimica fara sablon de nanofire de ZnO pe substrat de ITO. Nanofirele de ZnO au fost depuse prin cronoamperometrie la -0.9 V timp de 4 minute.

8. Depunerea stratului de polimer de tip p (HTL). Depunerea prin centrifugare de PEDOT si PEDOT:PSS la 6000 rpm timp de 30 secunde peste nanofirele de ZnO.

9. Depunerea stratului emisiv continand compusul IrQ(ppy)2. Dispersia compusului organometalic in TPD si depunerea prin centrifugare peste polimerul de tip p, la 2000 rpm si 30 secunde.

10. Depunerea polimerului de tip n si a catozilor metalici peste stratul emisiv. Centrifugarea polimerului BCP si Alq3 disolvati in solventi la 1000 rpm si 30 secunde. Evaporare termica de aur.

11. Masurarea caracteristicilor curent-tensiune in structurile multistrat obtinute. Determinarea caracterului Schottcky p-n intre nanofirele de ZnO si PEDOT.

12. Pulberea de IrQ(ppy)2 a fost inglobata in doua tipuri de polimeri conductori, TDP si CBP, in concentratii de 2 pana la 6% wt.

13. In ambii polimeri, electroluminescenta este portocalie ca amestec de culori intre electroluminescenta galben-verde si cea rosie provenita de la cele doua tipuri de liganzi.

14. Caracteristicile curent-tensiune in CBP:IrQ(ppy)2 arata trei domenii de conductie: a) una ohmica; b) una de sarcina spatiala si c) una fara centrii de captura.

15 Caracteristicile curent-tensiune in TPD:IrQ(ppy)2 sunt diferite deoarece TPD este polimer optic activ formand excitoni intrinseci a caror interactie cu excitonii produsi in moleculele de IrQ(ppy)2 conduc la un mecanism de conductie mai complicat pentru domeniul c) de conductivitate.16. Ca material conductor de electroni a fost folosit si Alq3, grosimea filmului fiind de 15 nm.

1. Iulia Corina Ciobotaru-doctorand in cadrul Universitatii Politehnice Bucuresti, cu teza „Materiale semiconductoare organice cu aplicatii in fotonica”. Rezultatele proiectului au fost integrate in teza de doctorat, doctoranda sustinad si doua seminarii generale si doua departamentale.

1. “Mechanisms of the charge transfer in IrQ(ppy)2-5Cl dual-emitter compounds”
S. Polosan, I.C. Radu

J. Nanosci. Nanotechnol. 13(7), 5203-5208 (2013).

2. “Dual emitter IrQ(ppy)2 for OLED applications: Synthesis and spectroscopic analysis”
I.C.Ciobotaru, S.Polosan, C.C.Ciobotaru
J. Luminescence145, 259-262 (2014).

3. "Structural characteristics of Iridium dual emitter organometallic compound"
S. Polosan, I.C. Ciobotaru, I. Enculescu, C.C. Ciobotaru
Journal of Materials Research29(23), 2898-2904 (2014).

4. "Electroluminescence of OLED based IrQ(ppy)2-5Cl organometallic compound: Theoretical considerations"
S. Polosan, I.C. Ciobotaru
J. Optoelectronics and Advanced Materials16(1-2), 87-92 (2014).

5. "Embedding of IrQ(ppy)2 organometallic compounds in polypyrrole conducting polymer for OLED`s applications"
I.C. Ciobotaru, E. Matei, C.C. Ciobotaru, S. Polosan
Synthetic Metals, 198,  323–328, (2014).

6. "Absorption, phosphorescence and Raman spectra of IrQ(ppy)2 organometallic compound"
S. Polosan, I.C. Ciobotaru, T. Tsuboi
Materials Chemistry and Physics, 162(15),  822-830 (2015).

7. “Templateless electrodeposition ZnO nanowires for charge transport optimization in OLED structures”
S. Polosan, E. Matei, I.C. Ciobotaru, C.C. Ciobotaru
Materials Research Express, 3,  105018 (2016).

8. “Charge Transport in CBP and TPD Thin Film Polymers Doped with IrQ(ppy)2 Phosphorescent Molecules”
C.C. Ciobotaru, I.C. Ciobotaru, S. Polosan
Journal of Electronic Materials, 47(2), 1490-1496 (2018).

9. "Crystallization properties of IrQ(ppy)2 organic complex films"
S. Polosan, C.C. Ciobotaru, I.c. Ciobotaru,T. Tsuboi
Journal of Materials Research, 32(9),  1735 (2017).

10. „Enhancement of the electroluminescence of organic light emitting devices based on IrQ(ppy)2 by doping with metallic and magnetic nanoparticles”
C.C. Cioboratu, I.C. Ciobotaru, G. Schinteie, R. Negrea, S. Polosan
Materials Science in Semiconductor Processing72, 78 (2017).

11. "Charge carrier traps in tris-(8-hydroxyquinoline) aluminum"
M. Secu, S. Polosan
J. Luminescence, 194, 91 (2018).

Au fost publicate 11 articole cotate ISI, cu un factor total de impact de 19.852 si 1 teza de doctorat pe baza rezultatelor proiectului.

1. I.C.Radu, S. Polosan, T. Tsuboi, "Dual Emitters for displays based on OLED compounds",12th International Balkan Workshop on Applied Physics, Constanţa, July 6-8, 2011.
2. S. Polosan, I.C.Radu, "Mechanisms of the charge transfer in IrQ(ppy)2-5Cl dual-emitter compounds", EMRS Spring Meeting, 14-18 Mai, 2012, Strasbourg, France.
3. I.C.Radu, S. Polosan, "Photophysical and magnetic properties of IrQ(ppy)2–5Cl for Organic Light Emitting Device applications", E-MRS Spring Meeting, 14-18 Mai, 2012, Strasbourg, France
4. I.C.Radu, C.C.Ciobotaru, S. Polosan, "Spectroscopy and structural analysis of Iridium intermediate compound", The 8th General Conference of Balkan Physical Union, 5-7 July 2012, Constanta, Romania.
5. S. Polosan, I.C.Radu, "Organometallic materials for low energy consumption OLED devices", The 8th General Conference of Balkan Physical Union, 5-7 July 2012, Constanta, Romania.
6. S. Polosan, I.C.Radu, "Organometallic Compounds and Their Applications", The 7th InternationalConference on Advanced Materials, ROCAM 2012, 28-31 August 2012, Brasov, Romania.
7. S. Polosan, I.C.Radu, "Phosphorescence of Iridium based organometallic compounds in Magnetic Field", 8th International Conference on Luminescent Detectors and Transformers of Ionizing Radiation -LUMDETR 2012, 9-14 Septembrie 2012, Halle, Germany.
8. I.C.Ciobotaru, S.Polosan, C.C.Ciobotaru, "Dual emitter IrQ(ppy)2 for OLED applications- synthesis and spectroscopic analysis", Sixth International Meeting on Molecular Electronics, December 3-7 2012,Grenoble, France.

9. S.Polosan, I.C.Ciobotaru, L.Stoflea, "Structural characteristics of IrQ(ppy)2 organometallic compound", Sixth International Meeting on Molecular Electronics, December 3-7 2012, Grenoble, France.
10. I.C. Ciobotaru ,S. Polosan, "Energy transfer in composite IrQ(ppy)2–5Cl: polystyrene layers", Third International Conference on Multifunctional, Hybrid and Nanomaterials, 21-23 May 2013, Sorrento, Italy.
11. S. Polosan, I.C. Ciobotaru, C.C. Ciobotaru, "Dual emitter organometallic compounds: thermal and structural characteristics", 13th International Balkan Workshop on Applied Physics, Constanta, Romania, 4-6 July, 2013
12. I.C. Ciobotaru, S. Polosan, C.C. Ciobotaru, H. Iovu, "New Ir(ppy)2 organometallic compound for OLED applications: synthesis and optical characterization", 13th International Balkan Workshop on Applied Physics, Constanta, Romania, 4-6 July, 2013
13. S. Polosan, I.C. Ciobotaru, C.C. Ciobotaru, "Iridium dual emitter organometallic compound: Thermal and structural analysis", 6th International Symposium on Flexible Organic Electronics (ISFOE13), 8‐11, July 2013, Thessaloniki, Greece.
14. I.C. Ciobotaru, S. Polosan, I. Enculescu, C.C.Ciobotaru, H. Iovu, "IrQ(ppy)2 in Poly(methyl-methacrylate) matrix for OLED applications", 6th International Symposium on Flexible Organic Electronics (ISFOE13), 8‐11 July 2013, Thessaloniki, Greece.
15. S. Polosan, "Electrochemical deposition of organometallic compounds", 10th International Conference on Electroluminescence and Optoelectronic Devices (ICEL 10), 31.08-3.09 2014, Cologne, Germany.

16. I.C. Ciobotaru, E. Matei, "Polypyrrole/ IrQ(ppy)2 composite films prepared by electrochemical deposition for OLED’s applications", 10th International Conference on Electroluminescence and Optoelectronic Devices (ICEL 10), 31.08-3.09 2014, Cologne, Germany.
17. I.C. Ciobotaru, S. Polosan, H. Iovu, "Influence of crystallization on the phosphorescence of IrQ(ppy)2 organometallic compound in OLED’s applications", E-MRS 2014 Spring Meeting, 25-31 May, 2014, Lille, France.
18. C.C. Ciobotaru, S. Polosan, "Embedding of IrQ(ppy)2 organometallic compounds in polypyrrole conducting polymer", E-MRS 2014 Spring Meeting, 25-31 May, 2014, Lille, France.
19. S. Polosan, "Electrochemical deposition of organometallic/polypyrrole composites for OLED applications", 14th International Balkan Workshop on Applied Physics, 2-4 July 2014, Constanta, Romania.
20. S. Polosan, "Charge transport optimization in OLED structures by using ZnO nanowires", ISFOE 15, 6-9 July, 2015, Thesalonic, Greece.
21. S. Polosan, E. Matei, I.C. Ciobotaru, C.C. Ciobotaru, "ZnO nanowires in organic light emitting diodes", The 15th International Balkan Workshop on Applied Physics, Constanta, 2-4 July, 2015.

Director de proiect:

Polosan Silviu - Dr. Senior Researcher I

Materials and Multifunctional Nanostructures

National Institute of Materials Physics

email: silv@infim.ro

 

tel: +40213690185

Ciobotaru Iulia Corina - Dr. Senior Researcher

Materials and Multifunctional Nanostructures

National Institute of Materials Physics

email: corina.ciobotaru@infim.ro

 

tel: +40213690185