Organic emitters play a vital role in determining the overall performance of organic light emitting diode (OLED) devices. Traditional fluorescent emitters can only achieve external quantum efficiency (EQE) of 5%, far below expectation; therefore many efforts have been spent on increasing the EQE of OLEDs. Phosphorescence, thermally activated delayed fluorescence, triplet–triplet annihilation, and hybridized local and charge transfer are the most widely applied approaches to harvest the 75% triplet excitons for luminescence. As for selecting or designing suitable emitters for practical applications, it is strongly demanded to have an overall view about emitters of high exciton utilizing efficiency (EUE) from molecule level, i.e., the four common approaches mentioned above and some latest ones of the doublet, singlet fission, triplet–polar annihilation, and rotationally accessed spin state inversion, and also from the aggregated state such as aggregation‐induced emission. In this review, the current progress of highly efficient emitters is presented, covering the chemical structures, the high‐EUE mechanisms in molecule level and aggregated state, and their applications in OLED devices. This review hopefully will illustrate highly efficient electroluminescent materials and their mechanisms, but more importantly, provide helpful information on how to design or select suitable emitters for specific OLED devices.

Flexible organic solar cells (FOSCs) were fabricated based on Ag nanowire/PET films with PEDOT:PSS composite electrodes. The influence of doping PH1000 with ethylene glycol on the photovoltaic performance has also been investigated. Optimum FOSCs exhibit a PCE of 10.30%. All the FOSCs show excellent flexibility after bending and even upon total folding.

Solution-processed organic light-emitting diodes (OLEDs) are much preferred for the manufacture of lowtemperature, low-cost, large-area, and flexible lighting and displaying devices. However, these devices with high external quantum efficiency are still limited, especially for blue ones. In addition, the molecular configurations of emitters are usually complicated, indicative of high costs. In this study, two simplestructured thermally activated delayed fluorescent emitters M1 and its polymer P1 were synthesized with acridine as a donor and benzophenone as an acceptor. Solution-processed OLEDs were prepared based on M1 and P1 as doped light-emitting layer, and M1-based doped device could achieve maximum external quantum efficiency of up to 20.6% with blue-light emission.

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Thermally activated delayed fuorescent (TADF) polymers are very suitable for fabricating highly efficient solution‐processed organic light emitting diodes (OLEDs). TADF homopolymers with simple structures are much preferred for preparation, but due to the triplet–triplet annnihilation, most TADF homopolymeric OLED exhibits lower external quantum efficiency (EQE) than its TADF repeating unit. Herein, two series small molecules (CzPhO and PxPhO) and their related mono‐polymers (PCzPhO and PPxPhO) are designed and synthesized for comparison. Among them, phenoxazine‐based materials show TADF properties compared to the carbazole‐based materials, which may be due to the enhanced electron donating ability of phenoxazine unit. In addition, the solution‐processed devices based on phenoxazine‐based polymer PPxPhO give excellent performance compared to their counterparts with the EQEmax of 11.8%.