Phosphorescent Organic Light-Emitting Devices: Working Principle and Iridium Based Emitter Materials

Abstract

Even though organic light-emitting device (OLED) technology has evolved to a point where it is now an important competitor to liquid crystal displays (LCDs), further scientific efforts devoted to the design, engineering and fabrication of OLEDs are required for complete commercialization of this technology. Along these lines, the present work reviews the essentials of OLED technology putting special focus on the general working principle of single and multilayer OLEDs, fluorescent and phosphorescent emitter materials as well as transfer processes in host materials doped with phosphorescent dyes. Moreover, as a prototypical example of phosphorescent emitter materials, a brief discussion of homo-and heteroleptic iridium(III) complexes is enclosed concentrating on their synthesis, photophysical properties and approaches for realizing iridium based phosphorescent polymers.

Recent Developments in the Application of Phosphorescent Iridium(III) Complex Systems

“…[189] In a host-guest system, three processes inducing the excitation of the phosphor are considered: the long-range Förster-type transfer of singlet excitons between matrix and guest, the short-range Dexter-type transfer of singlet and triplet excitons generated on the host to the dopant, as well as charge trapping and direct creation of singlet and triplet excitons on the guest. [190] In consequence of the strong spin-orbit coupling derived from the heavy metal atoms, both electrogenerated singlet and triplet excitons can be utilized for the emission. Therefore, an internal efficiency of 100% can be theoretically achieved.…”

“…Thereupon, the electron-hole pair formation occurs leading to an exciton generation (4). [2,182,185,190] The states of the tightly bound and localized excitons collapse and recombine under emission. [189] In a host-guest system, three processes inducing the excitation of the phosphor are considered: the long-range Förster-type transfer of singlet excitons between matrix and guest, the short-range Dexter-type transfer of singlet and triplet excitons generated on the host to the dopant, as well as charge trapping and direct creation of singlet and triplet excitons on the guest.…”

Synthesis and Electroluminescence of New Organic Emitters Based on a π-Conjugated 1,3,5-Triazine Core

“…[1][2][3][4] Large efforts to enable the high luminescence performance in OLEDs [5][6][7] have resulted in multilayered device architectures. On the contrary, the simple structure should have some advantages because it allows the brief fabrication of the device.…”

Full-Color LCD Microdisplay System Based on OLED Backlight Unit and Field-Sequential Color Driving Method

“…The OLED device turned on at a voltage of 3.5 V, and the white luminance under an applied voltage of 10 V was 500 cd/m 2 . Although the emitting performance of our OLED device was a little lower compared to state-of-the-art OLED devices because of the use of low-efficiency fluorescent emitting materials in our device, we think that there is much room for improvement in our system, by applying newly developed materials such as a phosphorescent emitting materials and high-efficiency charge injection materials [17][18][19]. Figure 7 shows the electro-optical response of the FSC driven OLED BLU at a frequency of 255 Hz.…”