Films OLEDs

A typical multilayer thin film OLED is made up of several active layers sandwiched between a cathode (often Mg/Ag) and an indium-doped tin oxide (ITO) glass anode. The cathode is covered by the electron transport layer which may be A1Q3. An emitting layer, doped with a fluorescent dye (which can be A1Q3 itself or some other coordination compound), is added, followed by the hole transport layer which is typically a-napthylphenylbiphenyl amine. An additional layer, copper phthalocyanine is often inserted between the hole transport layer and the ITO electrode to facilitate hole injection. 

The peculiar band structure of CPs is responsible for interesting optical properties including excitation driven visible light emission [or photolu-miniscence (PL)] in solution form. The use of CP for LEDs is inspired by possibility of electric field (E) driven luminiscence [or electroluminiscence (EL)] by the thin and defect free films of suitable CPs. The discovery of OLEDs dates back to 1989 and can be credited to Prof. Sir. Richard F. Friend (who is also known as Father of Organic Electronics ) and coworkers, who invented the first thin-film OLED based on electroluminiscent layer of PPV (only few nanometers thick) via a facile solution processing route... 

Mobile phone microphone spacer - film Ole Wolff Seokang Solder resistance - replaced PET... 

Since multiple electrical and optical functionality must be combined in the fabrication of an OLED, many workers have turned to the techniques of molecular self-assembly in order to optimize the microstructure of the materials used. In turn, such approaches necessitate the incorporation of additional chemical functionality into the molecules. For example, the successive dipping of a substrate into solutions of polyanion and polycation leads to the deposition of poly-ionic bilayers [59, 60]. Since the precursor form of PPV is cationic, this is a very appealing way to tailor its properties. Anionic polymers that have been studied include sulfonatcd polystyrene [59] and sulfonatcd polyanilinc 159, 60]. Thermal conversion of the precursor PPV then results in an electroluminescent blended polymer film. 

To date, most small molecule-based OLEDs are prepared by vapor deposition of the metal-organic light-emitting molecules. Such molecules must, therefore, be thermally stable, highly fluorescent (in the solid state), form thin films on vacuum deposition, and be capable of transporting electrons. These properties limit the number of metal coordination compounds that can be used in OLED fabrication. 

The discovery of the use of A1Q3 as an electron-transport-emitting layer is undoubtedly the most significant achievement in the research that led to the development of stable OLEDs.180,181 It is very stable and can be sublimed without decomposition at 350 °C,188 and its thin-film PL quantum efficiency at room temperature is about 32%, independent of film thickness between 10 nm and 1,350 nm.189... 

As a class of n-type organic semiconductors, PBI derivatives have received considerable attention for a variety of applications [312, 313], for example, for organic or polymer light-emitting diodes (OLEDs and PLEDs) [314, 315], thin-film organic field-effect transistors (OFETs) [316, 317], solar cells [318, 319], and liquid crystals [320]. They are also interesting candidates for single-molecule device applications, such as sensors [321], molecular wires [322], or transistors [141]. 

As mentioned in this review, AMPLEDs are especially attractive for motion picture applications. The Pay-Per-View effect in OLED displays reduces power consumption and extends operation lifetime. Motion picture applications also minimize image retention and optimize display homogeneity. AMOLED has been widely viewed as a promising display technology in competing with AMLCD and plasma displays. The dream of using organic semiconductor films for optoelectronic device applications has become a reality. 

Monodisperse analogs of such ir-electron systems, PPV oligomers (molecular glasses) were studied by Bazan and coworkers [217]. The films prepared from 192 by solution casting showed completely amorphous structure due to a tetrahedral structure of the molecule and OLEDs ITO/PVK/192/Al-emitted green light with an efficiency up to 0.22 cd/A (Chart 2.42). 

Although even lower WF can be achieved with, e.g., Yb (0 = 2.4 eV), the low reflectivity index of the latter makes it less suitable for OLED applications. The active metal Ca (0 = 2.60 eV) often has to be accompanied with other metals such as Al to increase the device lifetime. It is worth noting that the WF of the metals can be affected by their purity, their deposition method, and the surface structure, and the crystal orientation of the deposited films. 

Grubbs group reported a series of cross-linkable triarylamine-containing poly(norbor-nenes) (51) and investigated them as the HTMs in a bilayer OLED (Scheme 3.19) [94]. However, cross-linking was found to decrease the device performance due to the low Ts of the polymers and the poor film quality after UV irradiation. 

The electron-withdrawing dimesitylboryl substituted compound 5,5"-bis-(dimesitylboryl)-2, 2 5, 2"-terthiophene (BMB-3T, 108) was recently reported as an ETM [166], The molecule showed reversible two-peak reductions with high EA (3.05 eV) and can form amorphous films by vacuum evaporation. Using BMB-3T as the ETM for Alq3 OLEDs, a brightness of 21,400 cd/m2 and an EQE of 1.1% were obtained, compared to 13,000 cd/m2 and 0.9% for OLEDs without BMB-3T. 

---