Solution processed multilayer polymer light-emitting diodes based on different molecular weight host

Abstract

Solution processed multilayer polymer light-emitting diodes (PLEDs) based on different molecular weight host have been investigated. A PLED based on high molecular weight poly (vinyl carbazole) PVKH and low molecular weight poly (vinyl carbazole) PVKL, doped with iridium, tris(2-phenylpyidine) Ir(ppy)3 as a host-guest emitting layer (EML), shows a dramatic increase in device efficiency. When the PVKH was used as a hole transport electron blocking layer (HT-EBL), effective electron blocking was achieved, which leads to an increase exciton population in the phosphorescent zone. The use of low molecular weight PVKL as a host material in the top layer prevents barrier formation for hole transport from the poly(3,4-ethylenedioxy-thiophene) (PEDOT)–EBL to the EML. External quantum efficiency of 11%, current efficiencies of 38 cd/A, power efficiency of 13 lm/W and brightness of 7000 cd/m2, were obtained. The effect of the PVKH layer on the electrical and optical device characteristics was investigated. Simulation of the optical outcoupling using SETFOS 3.1 software is in agreed with the observed results and allowed us to predict the emissive dipole location and distribution in the EML layer. The effect of the PVKH on the exciton quenching by the electrodes was also investigated using time resolved fluorescence photon counting, which indicates weak exciton quenching by the PEDOT layer and the device enhancement predominantly achieved by exciton confinement in the emissive layer.

Singlet Generation from Triplet Excitons in Fluorescent Organic Light-Emitting Diodes

“…As yet, only poor lifetimes have been achieved, which suggest that it too has degradation problems, probably arising from the triplet energy being close to that required to break the ligand bonds, that is, a fundamental limitation. For PLED systems, the problem with blue phosphors is the fact that only few layer devices can be fabricated by sequentially solution deposition 2 ISRN Materials Science [13][14][15][16][17][18] so the high triplet energy host materials required cause serious charge injection problems. Although many groups are currently trying to tackle this problem, developing new materials sets for blue phosphorescent emitters using simple few layer device structures, alternatives to blue phosphorescent OLEDs are being sort.…”

Comparisons of the Efficiency of Excitation Energy Transfer by Singlet and Triplet Excitons in Carbazolyl-Containing Polymers

“…Фотопровiднi розчиннi полiмери надзвичайно пер-спективнi для практичного використання в ролi основи свiтлодiодiв [1][2][3][4][5][6][7] i кольорових дисплеїв [8][9]. Це пов'язано з можливiстю нанесення шарiв безпосередньо з розчинiв -шляхом поливу, а та-кож високотехнологiчними методами струминно-го [7] i трафаретного [5,8] друку, що значно зни-жує собiвартiсть виробiв порiвняно з використан-c ○ Ю.А.…”

“…Якщо не вжити спецiальних заходiв, то при кiмнатнiй температурi вони гинуть безвипромiнювально. То-му для пiдвищення квантової ефективностi свiтло-дiодiв пропонувалося вводити в випромiнюючий шар фосфоресцiюючи домiшки (так званi трипле-тнi емiтери), такi як металопорфiрини i органi-чнi комплекси важких металiв [2][3][4][5][6][11][12][13]. Завдя-ки сильнiй спiн-орбiтальнiй взаємодiї, iндукованiй атомом металу, в цих молекулах значно збiльшу-ється квантовий вихiд фосфоресценцiї (Φ Ph ).…”

“…Фотофiзичнi властивостi цього полiмеру дуже близькi до полi--вiнiлiлкарбазолу [14], який часто використовують як основу полiмерних свi-тлодiодiв [1,2,[4][5][6][7]. Для цього ми вимiряли спе-ктри люмiнесценцiї i визначили величини кванто-вих виходiв флуоресценцiї (Φ F1 ) i Φ Ph чистих плi-вок PEPC i його дiгалогенпохiдних -DClPEPC та DBrPEPC, вимiряли Φ Ph молекули Btp 2 Ir(acac) в плiвках полiстиролу (PS) i карбазолiлвмiсних по-лiмерiв, а також дослiдили спектри плiвок PEPC з двома домiшками -Btp 2 Ir(acac) i бензофенону.…”

Blue iridium complexes as electron trapping sites and efficient recombination centres in poly(N-vinylcarbazole) seen by spectrally resolved thermoluminescence

“…Either low molecular materials or polymers can be taken into consideration as a host for metal complexes [4][5][6][7][8]. Nevertheless, polymer hosts are more promising for use in large-area flexible devices due to advantages of solution processing technology such as easier and lower cost of fabrication [6,9,10].…”