| It was normally assumed that the efficiency of phosphorescent organic light-emitting diodes (PHOLEDs) were three times higher than that of the fluorescent organic light-emitting diodes (OLEDs). Therefore, studies on the PHOLEDs had been greatly intensified, containing with the materials exploitation and the device fabrication. In detail, host materials intrigued much interest as well as the light emitting materials in the emissive layer of the diodes. For the reasons of that the relative long-life of the phosphorescent extions were easily to get quenched when the devices were applied at the high voltage, that is the worst of lifting the overall efficiency of the device-making, hence, the emissive layer are mainly employed to adopt the host-guest matrix.Namely, phosphorescent are widely dopanted into the deliberately selected host materials at a small amount.The thesis was mainly composed of design and synthesis of the host materials for phosphorescent dopants and the device fabrication, general design approach was embarked on the mCP derivatives, which was originated from that mCP owned the triplet energy of2.9eV that was sufficient to work as the host material for the blue phosphor, in addition, structure of m-connected carbazole units ensured it possess the good hole transport properties, however, its tg was only59celsius, affording us the aim of basic modification, the original idea of the molecular design was to achieve the high Tg and high charge flux as well as maintaining the high Et, normally higher than the classical blue phosphor FIrpic(ET=2.67eV). Two series of seven novel compounds had been synthesized without literature statement. Targeted compounds are respectively examined by cyclic voltammetry (CV) analysis, UV absorption and photoluminescence spectrum analysis and thermo-gravimetric analysis on their studies of electro-chemical properties, photo-physical properties, and the thermal properties, genenaly, good thermal stability has been obtained, and the triplet energy level of CzM and TCzM exceed3.0eV, both of which were conducive to boost the overall efficiency of the blue OLEDs.Blue phosphorescent light emitting diodes based on the FIrpic had been fabricated by employing the CzM or TCzM as the host materials, and devices making process were arranged by incorporating mutil-functional layers though high vacuum deposition sequentially, two type of device conformation had been thoughtfully chosen via continuously trying. That were ITO/PEDOT:PSS (40nm)/NPB (12nm)/TCTA or mCP (10nm)/host+6%FIrpic (30nm)/TPBI (30nm)/LiF (1nm)/Al (200nm). Generally, better device proformance of both two materials had been achieved by using mCP as the blocking layer than TCTA. In addition, overall efficiency of devices based on CzM were much better than that of TCzM, and best device performance of the CzM/FIrpic system by employing the mCP as the blocking layer had been acquired with the current efficiency and power efficiency of22.18cd A-1and9.95lm W-1respectively.Devices adopting CzF or TCzF as the host materials for green Phosphor Ir(ppy)3had been carried out. efficiency of device based on CzF was better than that of TCzF under the same device conformation, besides, current efficiency and power efficiency of devices based on CzF increased from56.77cd A-1,33.25lm W-1to66.30cd A-1,46.24lm W-1after incorporating the functional layer of TCTA which served as the exciton blocking layer.Based on the much better devices performance obtained by incorporating the TCTA for Ir(ppy)3, we proposed the identical green phosphorescent device structures for CzN achieving the best current efficiency and power efficiency of62.25cd A-1and32.58lm W-1respectively. Red phosphorescent devices based on CzCN achieving the best current or power efficiency of7.87cd A-1or4.12lm W-1by stimulating the above-mentioned device making process. |
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