Polymer-based Organic Light-emitting Devices

Organic light-emitting diodes (OLEDs) have the advantages of simple structure, small size, low cost, low driving voltage, self-emission, quick response and so on, which is considered to be one of the most competitive display device for the next generation, and attract the interest of the researchers all over the world. Polymer organic light-emitting diode (PLED) has become the hottest topic in OLED area. For high machinability, polymers can be filmed simply through spin-coating or ink jet printing, which can fulfill large area and flexible display. There are many kinds of polymeric materials, whose electroluminescence in various colors including red, green and blue by changing the conjugate chain length, replacing groups and adjusting the structure or composition of main chains, etc. Moreover, PLED has simple fabrication process and low cost, which shows a promising market with strong competition. In this thesis, three color PLEDs were investigated respectively, and new methods were adopted to optimize the performance of the devices, which is practical to the development of the PLED.Green light-emitting PLED was investigated based on conventional double-layer device consisting of small molecular TPD/Alq3. Main concern is the balance of holes and electrons for the purpose of improving luminance efficiency. Hole transporting material TPD with low molecular mass was doped into insulating polymeric matrix PS as complex hole transport layer. With different doping concentration, the characteristics of photocurrent, temperature and lifetime were investigated, and the role of PS was analyzed.The study of blue emitting materials is a key point in OLED. Compared with the green emitting materials, the research of blue emitting materials is relatively backward, and their luminance, efficiency, stability, and color purity are far out of practical application, which limits the development of full-color display. Fluorene and its derivatives have a wide energy gap, which is beneficial to blue emission, and becomes the hot topic of blue emitting materials. In this work, PLED devices comprised of three novel fluorene-based polymers were fabricated and investigated. The optoelectronic performance of the PLEDs was analyzed, which provided reference in the developing of small molecule fluorene material。In the investigation of red light-emitting PLED, the light-emitting performance of the red emission polymer MEH-PPV was firstly investigated. The results showed that the introduction of hole blocking layer BCP improved device performance. Afterwards, DCJTB was doped into MEH-PPV and fluorene-based material PF60C10, and the difference of light-emitting performance between these two materials was analyzed and discussed.