S. Lengvinaite

Highly efficient blue organic light-emitting diode with an oligomeric host having high triplet-energy and high electron mobility

We report a high-efficiency blue organic light-emitting diode (OLED) with a solution-processed emissive layer composed of an oligomeric host of poly[3-(carbazol-9-ylmethyl)-3-methyloxetane] (PCMO) that possesses high triplet-energy and high electron mobility. The device exhibited a current efficiency of 40.4 cd A−1 with an external quantum efficiency (EQE) of 21.6% and power efficiency of 28.2 lm W−1 at 230 cd m−2 or 24.7 cd A−1, 10.3%, and 15.5 lm W−1 at 1 000 cd m−2. The high efficiency may be attributed to the host possessing a high electron mobility and lower electron injection barrier, resulting in a more balanced carrier-injection. Moreover, the high electron-mobility favors the transport of electrons, resulting in a more balanced carrier-injection in the emissive layer. The device efficiency has been further enhanced to 42.6 cd A−1 (22.9%, 29.7 lm W−1) at 124 cd m−2 or 28.8 cd A−1 (15.4%, 17.8 lm W−1) at 1 000 cd m−2 by pre-heating the emissive solution at an elevated temperature before spin-coating.

Crosslinkable Fluorene-Based Derivatives as Materials for Light Emitting Diodes

A series of cross-linkable fluorene-based derivatives have been synthesized by the multistep synthetic rout. Characterization of their structure by 1H NMR and mass spectrometry is presented. The synthesized materials were examined by various techniques including differential scanning calorimetry, thermogravimetry, UV, fluorescence and electron photoemission spectrometries. It is established that the new derivatives have large triplet energies and could be used as host materials in phosphorescent light emitting diodes. The device fabricated with the use of one of the new hosts reached a brightness of 1700 cd/m2 and a current efficiency of 3.4 cd/A.

Carbazol-3-yl Substituted Aromatic Amines Containing Crosslinkable Groups as Materials for Multilayer Light Emitting Diodes

A series of cross-linkable aromatic amines which are potential materials for hole-transporting layers have been examined by various techniques including differential scanning calorimetry, thermogravimetry, and electron photoemission spectrometry. Hole transport properties of the materials were tested in two-layer light emitting diodes with Alq3 as the electroluminescent and electron transporting material. One derivative was applied for the preparation of insoluble electro-active layers by cationic photo-initiated polymerization. Atomic force microscopy was used for the investigation of photopolymerized films which were tested as insoluble hole transporting layers in a device with Alq3.