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.

The inorganic CuSCN interlayer makes carbon-based perovskite solar cells more efficient and stable.

Two highly efficient red neutral iridium(III) complexes, Ir1 and Ir2, were rationally designed and synthesized by selecting two pyridylimidazole derivatives as the ancillary ligands. Both Ir1 and Ir2 show nearly the same photoluminescence emission with the maximum peak at 595 nm (shoulder band at about 638 nm) and achieve high solution quantum yields of up to 0.47 for Ir1 and 0.57 for Ir2. Employing Ir1 and Ir2 as emitters, the fabricated red organic light-emitting diodes (OLEDs) show outstanding performance with the maximum external quantum efficiency (EQE), current efficiency (CE), and power efficiency (PE) of 20.98%, 33.04 cd/A, and 33.08 lm/W for the Ir1-based device and 22.15%, 36.89 cd/A, and 35.85 lm/W for the Ir2-based device, respectively. Furthermore, using Ir2 as red emitter, a trichromatic hybrid white OLED, showing good warm white emission with low correlated color temperature of <2200 K under the voltage of 4-6 V, was fabricated successfully. The white device also realizes excellent device efficiencies with the maximum EQE, CE, and PE reaching 22.74%, 44.77 cd/A, and 46.89 lm/W, respectively. Such high electroluminescence performance for red and white OLEDs indicates that Ir1 and Ir2 as efficient red phosphors have great potential for future OLED displays and lightings applications.

The interface closely related to carrier transport plays a vital role in high-performance perovskite solar cells (PSCs). In this work, an ionic liquid (IL) 1-butyl-3-methylimidazole hexafluorophosphate (BMIMPF 6 ) has been introduced to simultaneously modify the TiO 2 and perovskite films, which improves the energy level matching and contact of the TiO 2 / CsPbI 2 Br interface as well as provides perovskite films with larger grain size, leading to more faster charge transfer and lower energy loss. Furthermore, the BMIMPF 6 modifier passivates the perovskite film defects and reduces defect-induced charge trapping and recombination in CsPbI 2 Br PSCs. Under dual-interface modification, the open-circuit voltage of the modified device increased to 1.22 V, and the power conversion efficiency (PCE) increased from 10.65 to 13.19%. Moreover, the unencapsulated modified devices exhibit an enhanced stability and maintain 91% of their initial PCE after 60 days of storage. This work has provided a strategy for efficient and stable PSCs by exploiting an IL to optimize the dual-interface at the same time.

The OLEDs, having mixed hosts sandwiched between hole- and electron-transporting hosts, exhibit an EQE exceeding the theoretical limit and extremely small efficiency roll-off.

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Four bipolar materials using 1,2,4-triazol derivative as an acceptor and carbazole as a donor were synthesized. They can be used not only as emitters to fabricate deep-blue OLEDs, but also as hosts to construct PhOLEDs.

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