Deep‐Blue Emission: Interfacial Potassium‐Guided Grain Growth for Efficient Deep‐Blue Perovskite Light‐Emitting Diodes (Adv. Funct. Mater. 6/2021)

Zhao

et al. 2021

Adv Funct Materials

117

Metal halide perovskites (MHPs) are a promising class of materials for next‐generation display and lighting applications. Since the first demonstration of bright electroluminescence (EL) from perovskite light‐emitting diodes (PeLEDs) in 2014, the EQEs of these devices increased from below 1% to more than 20% in merely four years. Despite the meteoritic rise of device efficiencies that placed the new LED technology in the spotlight, many scientific and technical challenges remain, preventing PeLEDs from advancing further into practical applications. The success of inorganic III‐V LEDs, or commercial LED technologies in general, lies in the ability to demonstrate the reliable generation of blue EL. For PeLEDs, high operational stability and efficient blue EL remain to be some of the most pressing goals. To accelerate further developments in these areas, the recent progress in the research of PeLEDs is reviewed. The authors attempt to establish preliminary connections between the degradation mechanisms and the strategies for improvements, exemplified by a selection of recent representative works in the field. Lessons learned from organic LEDs and perovskite solar cells point toward some of the most important directions. This progress report serves as a catalyst for further interdisciplinary research involving materials scientists, chemists, and physicists working together to realize operationally stable PeLEDs.

Section: Discussionmentioning

confidence: 99%

Section: Mhp Structures and Their Luminescent Propertiesmentioning

confidence: 99%

“…Next, we will briefly summarize the progress of blue PeLEDs with EL spectra peaked at ≤470 nm in the last five years. [ 25,118,123–127 ]…”

Section: Recent Progress On Blue Peleds: Dimensionality and Compositi...mentioning

confidence: 99%

“…However, it has been observed that, as the central wavelength of EL approaches these wavelengths, the peak EQEs and operational lifetimes drop considerably. [ 25,118,123–128 ]…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Toward Stable and Efficient Perovskite Light‐Emitting Diodes

Zhao

et al. 2021

Adv Funct Materials

117

“…[15] Currently, two common approaches are adopted to achieve blue emission, including i) bandgap engineering via mixing the halides (Br/Cl) in nanocrystals or 3D LHP films, [16,17] and ii) introducing long-chain organic cations, for example, phenyl-ethylammonium (PEA), butylammonium (BA), or phenyl-butylammonium (PBA) as spacers to restrict the grain growth and produce 2D perovskites with strong quantum confinement. [6,15] To date, various approaches (e.g., Asite cation engineering, [11] interfacial modification, [18,19] or trappassivation [16] methods) have been employed to develop blue PeLEDs. Notably, current high-performing sky-blue and blue PeLEDs are mostly realized by incorporating different types of long-chain organic molecules in LHP emitters.…”

Section: Introductionmentioning

confidence: 99%

Unravelling Alkali‐Metal‐Assisted Domain Distribution of Quasi‐2D Perovskites for Cascade Energy Transfer toward Efficient Blue Light‐Emitting Diodes

et al. 2022

Solution processable quasi‐2D (Q‐2D) perovskite materials are emerging as a promising candidate for blue light source in full‐color display applications due to their good color saturation property, high brightness, and spectral tunability. Herein, an efficient energy cascade channel is developed by introducing sodium bromide (NaBr) in phenyl‐butylammonium (PBA)‐containing mixed‐halide Q‐2D perovskites for a blue perovskite light‐emitting diode (PeLED). The incorporation of alkali metal contributes to the nucleation and growth of Q‐2D perovskites into graded distribution of domains with different layer number . The study of excitation dynamics by transient absorption (TA) spectroscopy confirms that NaBr induces more Q‐2D perovskite phases with small n number, providing a graded energy cascade pathway to facilitate more efficient energy transfer processes. In addition, the nonradiative recombination within the Q‐2D perovskites is significantly suppressed upon Na+ incorporation, as validated by the trap density estimation. Consequently, the optimized blue PeLEDs manifest a peak external quantum efficiency (EQE) of 7.0% emitting at 486 nm with a maximum luminance of 1699 cd m−2. It is anticipated that these findings will improve the understanding of alkali‐metal‐assisted optimization of Q‐2D perovskites and pave the way toward high‐performance blue PeLEDs.

Strategies Toward Efficient Blue Perovskite Light‐Emitting Diodes

Ren

Wang

Sun

et al. 2021

Adv Funct Materials

114

100

Substantial progress has been made in blue perovskite light-emitting diodes (PeLEDs). In this review, the strategies for high-performance blue PeLEDs are described, and the main focus is on the optimization of the optical and electrical properties of perovskites. In detail, the fundamental device working principles are first elucidated, followed by a systematical discussion of the key issues for achieving high-quality perovskite nanocrystals (NCs) and quasi-2D perovskites. These involve ligand optimization and metal doping in enhancing the carrier transport and reducing the traps of perovskite NCs, as well as the perovskite phase modulation and defect passivation in improving energy transfer and emission efficiency of quasi-2D perovskites. The strategies for efficient 3D mixed-halide perovskite and lead-free perovskite blue LEDs are then briefly introduced. After that, other strategies, including effective charge transport layer, efficient perovskite emission system, and effective device architecture for high light outcoupling efficiency, are further discussed to boost the blue PeLED performances. Meanwhile, the testing standard of blue PeLED lifetime is suggested to enable the direct comparisons of the device operational stability. Finally, challenges and future directions for blue PeLEDs are addressed.