By incorporating ultrathin (<0.1 nm) green, yellow, and red phosphorescence layers with different sequence arrangements in a blue fluorescence layer, four unique and simplified fluorescence/phosphorescence (F/P) hybrid, white organic light-emitting diodes (WOLEDs) were obtained. All four devices realize good warm white light emission, with high color rending index (CRI) of >80, low correlated color temperature of <3600 K, and high color stability at a wide voltage range of 5 V-9 V. These hybrid WOLEDs also reveal high forward-viewing external quantum efficiencies (EQE) of 17.82%-19.34%, which are close to the theoretical value of 20%, indicating an almost complete exciton harvesting. In addition, the electroluminescence spectra of the hybrid WOLEDs can be easily improved by only changing the incorporating sequence of the ultrathin phosphorescence layers without device efficiency loss. For example, the hybrid WOLED with an incorporation sequence of ultrathin red/yellow/ green phosphorescence layers exhibits an ultra-high CRI of 96 and a high EQE of 19.34%. To the best of our knowledge, this is the first WOLED with good tradeoff among device efficiency, CRI, and color stability. The introduction of ultrathin (<0.1 nm) phosphorescence layers can also greatly reduce the consumption of phosphorescent emitters as well as simplify device structures and fabrication process, thus leading to low cost. Such a finding is very meaningful for the potential commercialization of hybrid WOLEDs.

Combining emissions of hole- and electron-transporting layers simultaneously, a simple four-color hybrid white OLED realizes good white emission with a maximum CRI of 93–94 over a wide luminance range of 83.68–17 050 cd m−2, and also achieves a high EQE of 18.44%.

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High color stability and CRI (>80) pure exciplex WOLEDs with merely complementary colors of orange- and blue-exciplexes are realized with the application of spacers.

Owing to large steric hindrance, white light hyperbranched conjugated polymers exhibited the best electroluminescent performance with suppression of triplet–triplet annihilation.

TQT exhibits multifunctional luminescence characteristics, such as polymorphism and mechanochromic, with potential application in OLEDs. An extremely high photoluminescence quantum yield of 96.5% is achieved in CBP: TQT-G doped film.

Via π-expanded design strategy, a new robust SF system, Ex-DPP, has been successfully developed with high extinction coefficient, good molecular rigidity and excellent SF properties.

A non-doped device based on TPA1 demonstrates deep-blue emission at 430 nm with a CIEy value of 0.037 and an EQEmax value of 4.36%.