AIE-active, highly thermally and morphologically stable, mechanochromic and efficient solid emitters for low color temperature OLEDs

Abstract

Low color temperature (CT) lighting sources such as candle light are of significant importance to human health owing to their remarkably low suppression effect on the secretion of melatonin, which helps people relax. As an alternative to hydrocarbon-burning candles, spark- and smog-free low CT organic light-emitting diodes (OLEDs) are highly desired. So far, however, low CT OLEDs are mainly fabricated by doping technology with several rare-metal complexes and multiple emissive layers. Metal-free and non-doped low CT OLEDs remain challenging due to the notorious aggregation-caused quenching (ACQ) effect of traditional chromophores. In this contribution, two luminogens, namely BPA2TPAN and BNA2TPAN, consisting of bisarylamine and two triphenylacrylonitrile (TPAN) units, were designed and synthesized. Both luminogens exhibit typical aggregation-induced emission (AIE) characteristics with high solid-state efficiency up to 47.7%. They also possess high thermal stability and outstanding morphological stability as well as obvious mechanochromism. Non-doped OLED devices of the luminogens show physiologically friendly orange light (603, 606 nm) with low CT values of 2093 and 1883 K, which are much lower than those of incandescent bulbs (2000–2500 K) or even candles (∼1900 K), whereas their doped OLED devices emit yellow light (551, 559 nm) with significantly improved performance, whose maximal power, current and external quantum efficiencies are 8.3 lm W⁻¹, 12.2 cd A⁻¹ and 4.2%, respectively. These results suggest that AIE luminogens are suitable to fabricate metal-free and non-doped low CT OLEDs with rational molecular design; meanwhile, their electroluminescence can be easily modulated through doping technology.