第三列過渡金屬錯合物之光物理性質及其在有機發光二極體元件上的應用

Abstract

本論文主要在探討含第三列過度元素‚OsII‚錯合物之光物理性質的研究. 由於它具有重元素(heavy atom ),因此可以增強它系統間跨越(intersystem crossing )的效率,使得原先spin-forbidden 的磷光得以產生. 並利用各種儀器的架設來偵測這些發光體在激發態的光物理現象. 也由於這些第三列過渡金屬錯合物它具有很高的發磷光效率,所以亦被應用於有激發光二極體上(organic light-emitting devices ) 其內容主要分為六大章,第一章簡短的介紹關於有機發光二極體的歷史演進及其發光原理. 第二章則是實驗部分以及儀器架設的簡介. 第三章介紹中心金屬元素為Osmium(Os) 八面體的錯合物,由於在axial 的位置上有Iodide 取代,使得最低的激發態能階由原本典型metal-to-ligand (MLCT) 的transition 變成 mixed halide-to-ligand (XLCT~70%) 及 MLCT(~30%) 的transition.這種特性應用在OLED 上將增加其發光效率. 第四章及第五章介紹二價鋨金屬所形成之含2-吡啶吡唑族配基金屬錯合物的光物理性質‚藉由一些適當的且也系統的分子設計‚我們得到了藍色發光材料;最後,在第六章中,藉由加入離子而產生顏色上的變化,來當做metal ion phosphorescence probe.

Recently, strong phosphorescent organometallic compounds have been intensively investigated because of their potential applications in organic light-emitting devices (OLEDs). These materials, such as square-planar d8 complexes of PtIII and AuIII and octahedral d6 complexes of ReI, OsII, IrIII, and PtIV ions, commonly exhibit super- or long excited-state lifetimes and high luminescence efficiencies. Spin-orbital coupling, which is enhanced by the presence of heavy-metal ions incorporated at the core of these complexes, results in highly efficient intersystem crossing, as well as the breakdown of the spin-forbidden nature of phosphorescence. In addition, the stronger ligand field strength expected for these third-low elements makes the metal-centered d-d transitions relatively inaccessible from the lowest emitting state, so that the competing radiationless deactivation process may no longer play a crucial role in quenching the emission. As a result, much stronger room-temperature phosphorescence is normally observed in both the liquid and solid state. The aim of this article is to present some intriguing photophysical properties of a series of OsII complesex that have the potentials in the application of OLEDs. This thesis is organized as follows: we start in chapter 1 with a short introduction and general review of organic light emitting devices. Some instrumental setup and the methods for experiment that are likely to encounter while going through the whole thesis are then briefly discussed in chapter 2. We then consider in more details some of the OsII complexes including their photophysical properties, ligand field strength, ligand orientation effects, and their application in the OLEDs.