Study On Single-eml WOLED Utilizing ESIPT Complementary-color Emitters With AIE Characteristics

White organic light-emitting devices(WOLEDs) have drawn increasing attention due to their great potential for next generation solid-state lighting as well as full color display. Utilizing a single emissive layer(EML) by doping multiple chromophores in a suitable host is a relatively simple approach. However, this strategy generally requires strictly fine control of partial energy transfer(ET) from high-energy emitter(s) to low-energy emitter(s). Additionally, in single-EML type WOLEDs, emitters are generally doped in a host matrix, mainly because most dyes suffer from severe emission quenching in condensed state due to strong intermolecular interactions, which further complicates fabrication procedure control and increases cost. A possible strategy to circumvent all these issues is the use of single-EML incorporating aggregation induced emissions(AIE) emitters with two-complementary-color as well as completely blocked ET.Firstly, two yellow excited state intramolecular proton transfer(ESIPT) emitters(T4TB and T4AC) with AIE characteristics are screened as the low-energy components. Three blue emitters(O3TB, BMe and 1,8-D) are introduced as the high-energy components due to almost no spectrum overlaps. To verify whether the ET from blue to yellow emitters is prohibited, hybrid films of blue/yellow emitters with various mixing ratios are prepared and then investigated with steady- and transient-state photoluminescent spectrometry. And the corresponding results elucidated that the ET between the complementary emitters were effectively blocked, which provide foundation for fabricating WOLEDs.Finally, by regulating mixing ratios of blue/yellow emitters, six WOLEDs based on the following structure: ITO/NPB(50 nm)/Blue:Yellow(30 nm)/Alq3(20 nm)/Li F(1 nm)/Al(100 nm) are fabricated. All these WOLEDs exhibit stable white emission with small CIE variation in a wide operating range. Significantly, by increasing the operating voltage from 4 to 12 V, the CIE coordinate of WOLED(based on BMe:T4TB=6:1) is(0.303±0.005, 0.345±0.008).