Enhancing the kinetic stability and the lifetime of organic light-emitting diodes based on bipolar hosts by spiroconjugation
Journal
CHEMPHYSCHEM
Date
2018.05.02
Abstract
We examined how to enhance the lifetime of organic light-emitting diodes (OLEDs) based on bipolar host molecules ET-HT, where ET and HT refer to electron and hole-transporting units, respectively, by analyzing their thermodynamic and kinetic stabilities. Our DFT calculations reveal that the thermodynamic stability of ET-HT is determined by that of its anion, which is difficult to improve by chemical modifications of ET and HT. The kinetic stability of ET-HT can be enhanced by the spiroconjugation between ET and HT, which occurs when their pi-frameworks are extended and have an orthogonal arrangement. Green OLED devices fabricated by using ET-HTs with and without spiroconjugation, to find that the device with spiroconjugation has ~6 times longer lifetime than does the one without spiroconjugation.