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.

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Metal halide perovskite light-emitting diodes (PeLEDs) have been regarded as alternative candidates for full-color display applications with rapid progress to surge the external quantum efficiencies (EQEs) over 20%. However, in contrast to the high efficiencies of green, red, and near-infrared PeLEDs, the performance of their blue cousins is still lagging behind, especially the pure-blue one. Obtaining blue perovskite films with negligible nonradiative recombination loss and high stability is of great importance to realize efficient and spectrally stable blue PeLEDs. In this work, through partially replacing the toxic lead ions (Pb2+) with ecofriendly strontium ions (Sr2+) to tune the emission wavelength along with using passivation strategies, all-inorganic pure-blue perovskite films with a high photoluminescence quantum yield of 60.7% were achieved, which then delivered PeLEDs with a luminance of 510 cd m–2 and an EQE of 1.43%. The device yields a record radiance among the most efficient PeLEDs at 467 nm. In addition, the resultant PeLEDs displayed exceptional spectral stability during the electrical bias operation. Our work provides a promising avenue to develop environmentally friendly perovskite materials for efficient and spectrally stable pure-blue PeLEDs and beyond.

Quasi‐2D perovskites are enchanting alternative materials for solar cells due to their intrinsic stability. The manipulation of crystal orientation of quasi‐2D perovskites is indispensable to target efficient devices, however, the origin of orientation during the film fabrication process still lacks in‐depth understanding and convincing evidence yet, which hinders further boosting the performance of photovoltaic devices. Herein, the crystallizing processes during spin‐coating and annealing are probed by in situ grazing‐incidence wide‐angle X‐ray scattering (GIWAXS), and the incident‐angle‐dependent GIWAXS is conducted to unveil the phase distribution in the films. It is found that undesirable lead iodide sol–gel formed intermediate phase would disturb oriented crystalline growth, resulting in random crystal orientation in poor quasi‐2D films. A general strategy is developed via simple additive agent incorporation to suppress the formation of the intermediate phase. Accordingly, highly oriented perovskite films with reduced trap density and higher carrier mobility are obtained, which enables the demonstration of optimized quasi‐2D perovskite solar cells with a power conversion efficiency of 15.2% as well as improved stability. This work paves a promising way to manipulate the quasi‐2D perovskites nucleation and crystallization processes via tuning nucleation stage.

The innate capability of direct heat-electricity conversion endows thermoelectric (TE) materials great application potential in the fields of low-grade heat harvesting, solid-state cooling, and sensing. Recently, the rapid development of...

Balanced charge injection is key to achieving perovskite light-emitting diodes (PeLEDs) with a low efficiency roll-off at a high brightness. The use of zinc oxide (ZnO) with a high electron mobility as the charge transport layers is desirable; however, photoluminescence (PL) quenching of a perovskite on ZnO always occurs. Here, a quasitwo-dimensional perovskite on ZnO is explored to uncover the PL quenching mechanism, mainly ascribed to the deprotonation of ammonium cations on the ZnO film in association with the decomposition of low-dimensional perovskite phases. Surprisingly, crystal planedependent PL quenching results indicate that the deprotonation rate strongly correlates with the crystal orientation of the ZnO surface. We developed a strategy for suppressing perovskite PL quenching by incorporating an atomic layer deposited Al 2 O 3 onto the ZnO film. Consequently, an efficient inverted PeLED was achieved with a maximum external quantum efficiency of 17.7% and a less discernible efficiency roll-off at a high current density.

Implementation of ammonium halides to trigger low-dimensional perovskite formation has been intensively investigated to achieve blue perovskite light-emitting diodes (PeLEDs). However, the general roles of the incorporated ammonium cations on...

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.