Triarylphosphine oxide–phenanthroline molecular conjugate as a promising doped electron-transport layer for organic light-emitting diodes

Abstract Over the past three decades, transparent high electron mobility molecular materials have attracted intensive research efforts for organic light-emitting diodes as electron-transport layer for the sake of low working voltage, high power efficiency and operational stability. However, developing high-performing electron-transport materials presents a demanding challenge owing to difficulties in synthesis, purification and/or processing. In this contribution, we show that n-doping a simple and facilely available phenanthroline derivative, namely 3-(6-diphenylphosphinylnaphth-2-yl)-1,10-phenanthroline Phen-NaDPO with a high Tg of 116 °C, is capable of greatly increasing the electron conductivity up to 3.3 × 10−4 S m−1. The characterization of the blue sky fluorescent and green phosphorescent OLEDs involving this doped electron-transport layer Phen-NaDPO:50% wt Cs2CO3 revealed comparable performances to the analogue BPhen (Tg ≈ 66 °C) OLEDs. For instance, the resulting sky blue fluorescent OLEDs provided ca. 15 cd/A, 13 lm/W @1000 cd m−2 & t95 ≈ 167 h @1000 cd m−2. The present finding shows that the doped Phen-NaDPO may be a robust electron-transport material for optoelectronics.