الفهرس 
SUMMARYOnly 14 pages are availabe for public view
 |  | from | 131 |  |  |
| | | from | 131 | | |
Abstract
Organic light emitting diodes (OLED) have attracted great attention in both fundamental research and device fabrication because of their potential application to display components [1–3] with low-operating voltage, low-power consumption, low cost, self-emission, and a capability for multicolor emission by selection of emissive materials ]4,5[. Tremendous progress has been made, and OLED technology is expected to show great impact on the future of general lighting application and flat-panel displays [1,6,7].
An OLED panel consists of a layer of organic, light–emitting material sandwiched between two conductors (an anode and a cathode). This diode layer emits light when an electric current is passed through it. Because the organic material used in an OLED panel emits its own light when charged, there’s no need for a separate back light. Light emitting in OLED is the result of the recombination of electron and hole in light emitting layer, which are injected from cathode and anode [2,8].
Tang and Van Slyke [2] described bright green thin-film small-molecular OLEDs (SMOLEDs) based on tris(8-hydroxyquinoline) Al (Alq3) that were deposited by thermal vacuum evaporation. Friend and coworkers [6,10] reported yellow–green polymer LEDs (PLEDs) based on poly(p-phenylene vinylene) (PPV) that were fabricated by spin coating a precursor polymer onto the transparent conducting anode and converting the precursor to PPV by heating it.
Although OLEDs are being commercialized in a large number of products [9], the outstanding challenges are in their overall power efficiency and long-term stability which remain at high brightness, These challenges are intimately tied to the dynamics of the basic excitations in these materials and devices, namely singlet excitons (SEs), triplet excitons (TEs), and p- and p+ polarons, to which the electrons e- and holes h+, respectively, relax as they are injected from the electrodes into the organic layers of the OLED.