Combinatorial Development of Blue OLEDs Based on Star Shaped Molecules

Abstract

In this paper we describe the use of combinatorial vapor deposition techniques for the optimization of blue organic light emitting diodes (OLEDs). In these devices the star shaped molecule 1 with a triphenylamine core and three fluorene side groups serves as hole transport and emitting layer. Compound 2 with a much lower lying HOMO and a larger bandgap is used as hole blocking layer. Using combinatorial vapor deposition 42 OLEDs with thickness gradients of both the hole transport and the hole blocking layer have been simultaneously prepared on one substrate. The physical characterization of the devices clearly shows that a hole blocking layer of the star shaped molecule 2 is necessary in order to obtain pure blue emission with CIE coordinates of x = 0.15 and y = 0.15. A thickness of only 5 nm of the blocking layer is sufficient, and with increasing layer thickness the brightness of the blue devices drops. The blue devices exhibit a brightness of 400 cd m–2 and a luminous efficiency of 2 cd A–1. The thickness variations of both the hole transport and the hole blocking layer have been made in one combinatorial evaporation experiment on a single substrate using a set of movable masks. This demonstrates how efficient combinatorial methods can be used for the development of OLEDs.

Электронное Строение И Спектры Трифениламинов, Функционализированных Фенилэтинильными Группами

“…Звездообразные производные трифениламина на се-годняшний день привлекают значительное внимание исследователей в связи с перспективными оптическими свойствами этих соединений [1][2][3][4][5] и их высокой термо-и электростабильностью [6,7]. Свободный (нефункци-онализированный) трифениламин является оптически " прозрачным" материалом и лишь слабо поглощает электромагнитное излучение в ближнем УФ диапа-зоне (в области 250−340 nm) [8].…”

Novel aromatic polyamides containing 2‐diphenylamino‐(9,9‐dimethylamine) units as multicolored electrochromic and high‐contrast electrofluorescent materials

“…They have excellent quantum efficiencies, electron mobilities and thermal stabilities. Moreover, fluorene‐triphenylamine derivatives received extra attention as they could be used as hole‐transmission emitters in the OLEDs . Inspired by the attractive properties associated with the triphenylamine and fluorene units, we have reported a series of polyamides containing 2‐diphenylamino‐(9,9‐dimethylfluorene; DPA‐MeF) group as potential electrochromic and electrofluorescent materials .…”

“…Moreover, fluorene-triphenylamine derivatives received extra attention as they could be used as hole-transmission emitters in the OLEDs. 37 Inspired by the attractive properties associated with the triphenylamine and fluorene units, we have reported a series of polyamides containing 2-diphenylamino-(9,9-dimethylfluorene; DPA-MeF) group as potential electrochromic and electrofluorescent materials. 38 These polyamides exhibited stable electrochemical and electrochromic properties for the reason that the para-position of triphenylamine is well protected.…”

Electrochromic and electrofluorochromic polyimides with fluorene-based triphenylamine

“…35 These derivatives possess enhanced hole-transporting abilities and emitting efficiency. 36,37 Therefore, these derivatives could be used as promising electroactive fluorophores in stimuli-responsive fluorescence switching materials which have attracted great interest recently for the potential applications in sensors and displays. [38][39][40] TPA þ is an effective fluorescence quencher and thus the on/off states of fluorescence could be effectively modulated by switching the reduction/oxidation states of TPA.…”