Aromatic-Amine-Containing Polymers for Organic Electroluminescent Devices

Abstract

We investigated the suitability of aromatic amine-containing polymers as active layers in organic electroluminescent devices. Polymers used in this study include poly(N-vinylcarbazole) (PVK), poly(N-substituted methacrylamide)s, poly(methacrylate) and poly(arylene ether)s. The device structures are a double-layer-type and a single-layer type. The double-layer-type devices consist of a polymer hole transport layer and an electron-transporting emitter layer. High luminance of over 14,000 cd/m 2 was observed for some double-layer devices using the polymer hole transport layer. Single-layer devices with dye-dispersed PVK emitted white light with a luminance of over 4000 cd/m 2 . This demonstrates that dye-dispersed polymer systems are quite useful to obtain white light.Organic electroluminescent (EL) devices are the subject of study by many researchers because of their potential application as light-emitting devices which operate at low drive voltages. These devices are injection-type, in which carriers, such as electrons (radical anions) and holes (radical cations), are injected into the organic emitter layer where they recombine. It is, therefore, necessary for the component organic materials to possess carrier-transporting properties as well as fluorescence properties.Although electroluminescence in organic molecules have been known since the 1960's (7), a major breakthrough was made in the 80's by Tang and VanSlyke who developed a device exhibiting practical brightness (2). Their device consisted of a double layer structure with an organic hole transport layer and a luminescent metal complex layer. The hole transport layer plays an important role in transporting holes and blocking electrons, thus preventing electrons from moving into the electrode without recombining with holes. Aromatic diamine derivatives, such as yV^V-diphenyl-,^V-bis(3-methylphenyl)-l,r-biphenyl-4,4'-diamine (TPD), have been widely used as a hole transport layer because of their high hole mobilities (10" 3 cm 2 /Vs) and good

A Novel Sterically Bulky Hole Transporter to Remarkably Improve the Lifetime of Thermally Activated Delayed Fluorescent OLEDs at High Brightness

“…To evaluate the performance of novel HTLs, three types of OLED devices based on 4CzIPN were fabricated with the structure of [ITO (100 nm)/triphenylamine‐containing polymer: 4‐isopropyl‐4‐methyldiphenyl‐iodonium tetrakis(pentafluorophenyl)borate (PPBI) (20 nm)/HTL (20 nm)/mCBP: 15 wt % 4CzIPN (30 nm)/DBT‐TRZ (10 nm)/1,4‐di(1,10‐phenanthrorin‐2‐yl)benzene (DPB): 20 wt % 8‐quinolinolato lithium (Liq) (40 nm)/2‐(2′,2′′‐bipyridine‐6′‐yl)phenolate (Libpp) (1 nm)/Al] (Device 1). We used DBT‐TRZ as the hole‐blocking layer and DPB as the ETL in order to obtain long operation stability (Figure ).…”

Influência de diferentes solventes utilizados na deposição de filme de poli(9-vinilcarbazol) em dispositivos OLEDs

“…31,32 A energia do HOMO do PVK é 5,8 eV, enquanto que o PEDOT:PSS apresenta uma função trabalho de 5,1 eV, ou seja, existe uma barreira de energia de 0,7 eV comparativamente entre as duas camadas, ainda que tenham propriedades eletrônicas de transporte de buracos análogas. 33,34 É oportuno também mencionar que o recozimento do PEDOT:PSS em diferentes temperaturas mostrou a redução da resistência elétrica e o aumento da função trabalho, de modo que as propriedades elétricas dos polímeros são dependentes da sua morfologia. 35 Além das medições de resistência elétrica foram realizadas análises ópticas, para verificar a morfologia presente nos diferentes filmes de PVK depositados sobre os filmes de PEDOT:PSS/ITO/ vidro.…”

“…A faixa aproximada de 500 a 550 nm corresponde à cor verde no espectro eletromagnético, sendo que é nesta faixa que ocorre a eletroluminescência dos dispositivos. 33 Com a mudança do solvente orgânico na deposição dos filmes de PVK verificamos que ocorreu uma variação no desempenho dos dispositivos e também comprometeu significantemente os comprimentos de onda da luz emitida pela eletroluminescência, incluindo um deslocamento pouco significativo no comprimento de onda do pico principal de emissão, como demonstramos na Figura (5). Na Figura 5, as curvas dos OLEDs foram normalizadas no gráfico maior, enquanto que no gráfico menor foram mantidas as curvas conforme obtidas diretamente do software do equipamento.…”

Unique Solid‐State Emission Behavior of Aromatic Difluoroboronated β‐Diketones as an Emitter in Organic Light‐Emitting Devices

“…Based on the obtained photophysical properties, we fabricated three types of OLEDs by using 3-Phe@Ph-dopedh ost films as the emission layers (EMLs). We used 3,3'',5,5'-tetra(3-pyridyl)-1,1';3'1''-terphenyl (B3PyPB) [16] as an electron transporter and lithium fluoride (LiF) as an electron-injection layer.W ei nserted aT CTAl ayer between the hole transporter (di(naphalene-1-yl)-N,N'-diphenylbenzidine (NPD)) and EML to achieve stepwise hole injection into the EML because 3-Phe@Ph has av ery deep I p value of 6.5 eV.T he structure of the resultant devices was indium tin oxide (ITO;1 30 nm)/triphenylamine-containing polymer,4 -isopropyl-4-methyldiphenyliodonium tetrakis(pentafluorophenyl)borate (PPBI; [17] 20 nm)/NPD (10nm)/TCTA (10 nm)/3 wt % 3-Phe@Ph-dopedh ost film (20 nm)/B3PyPB (40 nm)/LiF( 0.5 nm)/Al( 100 nm). The energy diagram of this devicei ss hown in Figure S3.…”