Metal halide perovskites have attracted considerable interest for their potential applications in high‐definition displays owing to their narrowband emission, wide color gamut (≈140%), near‐unity photoluminescence efficiency, and cost‐effective solution processability. Extensive efforts have led to the external quantum efficiency of state‐of‐the‐art perovskite light‐emitting diodes (PeLEDs) to exceed 20%. However, there are several obstacles, such as poor working stability, low efficiency, and low luminance, of pure‐blue and pure‐red light‐emitting devices that delay their commercial application. Addressing these issues requires a deep understanding of the photoluminescence effect as well as the bottlenecks in the process. Here, the fundamental working principle, carrier recombination, and light outcoupling properties of PeLEDs are described. The performance improvement strategies of PeLEDs based on defect engineering, perovskite crystallization, charge injection balancing, and quantum confinement are discussed. Furthermore, the challenges of PeLEDs in pure‐color light emission, working stability, and toxicity are reviewed and discussed.

It is a big challenge to achieve pure-blue (≤470 nm) perovskite light-emitting diodes (PeLEDs) with high efficiency and stability. Here, we report pure-blue (electroluminescence at 469 nm) PeLEDs with a full width at halfmaximum of 21 nm, high external quantum efficiency of 10.3%, luminance of 12 060 cd m −2 , and continuous operation half-life of 25 h, representing the stateof-the-art performance. This design is based on strongly quantum confined CsPbBr 3 quantum dots (QDs) with suppression of Auger recombination, which was enabled by inorganic ligands, replacing initial organic ligands on the QDs. The inorganic ligand acts as a "capacitor" to alleviate the charge accumulation and reduce the exciton binding energy of the QDs, which suppresses the Auger recombination, resulting in much lower efficiency roll-off of PeLEDs. Thus, the devices maintain high efficiency (>10%) at high luminance (>2000 cd m −2 ), which is of considerable significance for the display application.

Solution‐processed light‐emitting diodes (LEDs) show great potential for low‐cost fabrication of large‐area display panels, but the efficient perovskite LEDs (PeLEDs) cannot be achieved by all solution process, because the perovskite emitter is easily destroyed by subsequent solution. In particular, the solution‐processed PeLEDs with blue emission wavelength in 460–470 nm (pure‐blue, meeting Rec. 2020 standards) still is inferior. Here, highly efficient and stable pure‐blue PeLEDs are achieved by all solution process based on colloidal perovskite quantum dots and difunctional ZnO (D‐ZnO) nanocrystals. The D‐ZnO nanocrystals are obtained by a ligand strategy of phenethylammonium bromide, which not only repairs the perovskite surface destroyed by the solvent of the D‐ZnO solution, but also enables the balanced charge injection to suppress Auger recombination. The PeLED presented pure‐blue emitting at 470 nm wavelength, a maximum luminance of 11 100 cd m‐2, and external quantum efficiency of 8.7% (record efficiency for pure‐blue emission). The device also showed a continuous operation half‐lifetime of 35 h at luminance of 100 cd m‐2.

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Quantum dots (QDs) photodetectors with low cost, tunable spectral response range, the great possibility of multiple-exciton generation, and excellent detective performance have shown significant advantages in the fields of optical...