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Electroluminescence (EL) efficiency of perovskite light‐emitting diodes (PeLEDs) based on a few square millimeters has improved significantly in recent years. Nevertheless, the EL efficiency of PeLEDs would plunge once the active area is enlarged from a millimeter to even a subcentimeter due to the unsmooth energy transfer process among the edge region with numerous nonradiative recombination centers. Herein, an intriguing strategy is developed to realize high‐quality quasi‐2D perovskite thin film via tuning perovskite precursor rheological properties as well as modulating the substrate surface tension. The perovskite crystallization process is retarded by incorporating a strong chelating ligand into its precursor. Hydroxylamine‐O‐sulfonic acid, containing a sulfonic acid group and an amino group, acts as a strong chelating agent with lead ions (Pb2+), which exhibit great synergistic potential in defect passivation and crystallization modulation. As a result, a large‐area (25 cm2) quasi‐2D PeLED achieves an external quantum efficiency of 20.7% with uniform emitting characteristics, a record value among analogous same‐size PeLEDs. The work may pave the way to realize high‐performance large‐area perovskite optoelectronic devices. [ABSTRACT FROM AUTHOR]

Perovskite light‐emitting diodes (PeLEDs) are promising technologies for advanced display and lighting source applications. Alongside tremendous efforts to improve efficiency, developing flexible devices could potentially enable PeLEDs compatible with wearable, foldable, bio‐integrated, and other intriguing functionalities. However, the flexible PeLEDs currently have not received enough attention. The overall performance still lags behind the rigid one, mainly attributed to the lack of mechanically stable perovskite thin films with desirable optical and electrical properties. Herein, a self‐healing strategy to achieve flexible perovskite films with improved mechanical reliability and optoelectrical properties is proposed. A multi‐functional silane molecule of (3,3,3‐trifluoropropyl) trimethoxysilane (TFPTMS) is incorporated into a perovskite precursor, which could undergo an in situ cross‐linking process and generate a flexible Si–O–Si network within the perovskite films. In addition, the reversible hydrolysis and condensation reactions and the fluorinated alkyl chains endow the perovskite films with self‐healing capability. Accordingly, the synergistic influences contribute to high‐efficiency flexible PeLEDs with an external quantum efficiency (EQE) of 16.2%. Moreover, 75% of the initial efficiency value is reserved even after 1000 bending cycles. This work paves a way to rationalize flexible perovskite thin films for various optoelectronic applications. [ABSTRACT FROM AUTHOR]

Inkjet printing is a powerful technology for realizing high‐density pixelated perovskite light‐emitting diodes (PeLEDs). However, the coffee‐stain effect in the inkjet printing process often leads to uneven thickness and poor crystallization of printed perovskite features, which deteriorates the performance of PeLEDs. Here, a strategy is developed to suppress the coffee‐stain effect via enhancing Marangoni flow strength. An interfacial poly(vinylpyrrolidone) (PVP) layer is incorporated to tune the surface tension of the underlying hole transport layer (HTL) and enhance the perovskite crystallization. The substrate temperature is also carefully controlled to tune the printing solvent evaporation rate rationally. By optimizing the thickness of the PVP layer and the temperature of the printing stage, the coffee‐stain effect is dramatically restrained. In addition, the interfacial insulating PVP layers play a positive role in suppressing leakage current level of PeLEDs by avoiding any direct electrical contact between HTL and electron transporting layer. Finally, an inkjet‐printed PeLED with a brightness of 3640 cd m–2 and external quantum efficiency of 9.0% is achieved. This work highlights the availability of inkjet‐printing technology for fabricating patterned PeLEDs in information display applications. [ABSTRACT FROM AUTHOR]

The charge transport layer is a critical functional component in perovskite light emitting-didoes (PeLEDs). Metal oxide semiconductors (MOSs) are attractive charge transport materials owing to their advantages of robust stability, high carrier mobility, high transparency, as well as low cost. However, because of the complex mutual chemistry disturbance between the metal oxide and luminescent halide perovskites, there are severe charge quenching and even decomposition of the perovskite layers. Therefore, the advance of MOSs as charge transport layers in PeLEDs is still confined within selective cases. It is a prerequisite to gain depth insight into the interfacial contact between perovskites and MOSs from surface chemistry reactions and charge quenching before the realization of MOSs charge transport layers for constructing efficient and stable PeLEDs. In this review, we started with a brief introduction to perovskite materials and the development of PeLEDs. Then, we highlighted the importance of the interfacial contacts between perovskite and charge transport layers, followed by summarizing the progress of PeLEDs using MOSs as charge transport layers from the aspects of surface reaction, crystallization, quenching mechanism, charge injection, and operational stability. We also proposed possible research directions on engineering MOSs charge transport layers that would further improve the performance of PeLEDs. [Display omitted] • Metal oxide materials as charge transport layers in perovskite light emitting-didoes are discussed comprehensively. • The complex mutual chemistry disturbance between the metal oxide and perovskite materials is highlighted. • The advances are summarized from the aspects of surface reaction, crystallization, quenching mechanism, and operational stability. • Research directions on engineering metal oxide layers for stable devices are proposed. [ABSTRACT FROM AUTHOR]