摻入電洞傳輸材料於固態有機發光電化學元件之發光層以改善元件特性

Abstract

離子性過渡金屬錯合物為材料之固態發光電化學元件，其具備很多的優點，例如：元件效率高、操作電壓低、元件結構簡易。為了改善使用離子性過渡金屬錯合物為材料之發光電化學元件的元件效率，提高載子平衡使得複合區域達到在發光層較中心的位置將是重要的議題。在本研究中，摻入電洞傳輸材料於電化學發光元件之發光層，其結果顯示出改善了元件效率及特性表現。與未摻入電洞傳輸材料元件(neat film)相比較下，當摻入電洞傳輸材料GK103(12 %)於釕錯合物之電化學發光元件，其光輸出和外部量子效率之峰值分別呈現出1.9倍和1.5倍之增強。而且，當電化學發光元件摻入電洞傳輸材料後，其元件穩定之外部量子效率可達2倍增強。元件特性表現能得到優化，其原因為電化學發光元件摻入電洞傳輸材料後，使得復合區位置能移動到較中心的發光層區域，因此當摻雜層不斷延伸時，激子猝熄的現象可以達到降低的效果。本研究為了證實當電化學發光元件摻入電洞傳輸材料後，其複合區位置會隨著時間而變化，因此搭配微共振腔效應來進行擬合並解釋其物理特性改善了元件表現。這些結果顯示出使用離子性過渡金屬錯合物為主體材料摻入電洞傳輸材料之電化學發光元件，是一個切實可行的方法改善了載子平衡，進而提升增強了光輸出及外部量子效率。

Solid-state light-emitting electrochemical cells (LECs) based on ionic transition metal complexes (iTMCs) have several advantages such as high efficiency, low operation voltage and simple device structure. To improve device efficiency of iTMC-based LECs for practical applications, improving carrier balance to achieve a centered recombination zone would be an important issue. In this work, incorporating a hole-transport material (HTM) into the emissive layer of iTMC-based LECs is shown to improve device performance. When mixed with an HTM (12%), the LECs based on a Ru complex exhibit 1.9X and 1.5X enhancement in peak light output and peak external quantum efficiency (EQE) as compared to neat-film devices. Furthermore, over 2X enhancement in stabilized EQE can be achieved in LECs mixed with an HTM. It is attributed to that more centered recombination zone in LECs mixed with an HTM is beneficial in reducing exciton quenching in the recombination zone approaching extended doped layers. Estimating temporal evolution of recombination zone in the LECs mixed with an HTM by employing microcavity effect is demonstrated to confirm the physical origin for improved device performance. These results reveal that incorporaing of an HTM in the emissive layer of LECs based on an iTMC is a feasible way to improve carrier balance and thus enhances light output and device efficiency.