Search

For the first time, a Co and Fe bimetallic metal‐organic framework (BMOF) nanosheet array (NSA) employing 5,5′,5′'‐(1,3,5‐triazine‐2,4,6‐triyl)tris(azanediyl)triisophthalic acid (H6TDPAT) as the organic ligand is in situ controllably self‐assembled on iron foam (IF). The obtained IF@CoFe‐TDPAT NSA exhibits an oxygen evolution reaction (OER) activity much superior to most reported catalysts and even Ru and Ir‐based ones and hydrogen evolution reaction (HER) activity higher than most metal‐organic framework (MOF)‐based catalysts. The excellent bifunctional activities are ascribed to the superhydrophilic (3D) vertically aligned, interconnected NSA of CoFe‐TDPAT MOF with in situ activated coordinatively unsaturated metal sites remarkably enhancing OH− and H2O adsorption, accelerating electron transfer and transport, and facilitating O2/H2 diffusion. When adopted as a bifunctional electrode for overall water splitting, it achieves 300 mA cm−2 at 1.753 V and exhibits negligible current decay after 100 h. This performance is the highest of recently reported noble‐metal‐free water electrolyzers, and even much higher than those using commercial noble metal‐based catalysts. This work offers an economical, facile, and controllable strategy to fabricate low‐cost, highly efficient, and bifunctional BMOF nanostructured array electrodes for large‐current‐density water splitting, and also sheds light on the mechanisms for in situ self‐assembly and outstanding OER and HER performance of 3D free‐standing complex‐organic‐ligand‐based BMOF nanoarchitectures. [ABSTRACT FROM AUTHOR]

Perovskite light‐emitting didoes (PeLEDs) have shown considerable potential in solution‐processable display applications. However, the performance of blue PeLEDs in terms of efficiency and stability hinders their practicality on account of severe trap‐mediated nonradiative recombination losses and halide phase segregation. To ameliorate these issues, mixed‐halide sky‐blue perovskite materials are strategically modulated through crystal defect passivation with a trifurcate isocyanate oligomer, which leads to the synergistical suppression of charge trap density and halide ion migration. The proposed approach enables the performance improvement for sky‐blue PeLEDs, exhibiting a peak external quantum efficiency of 14.82% and spectrally stable emission at 487 nm. In addition, prolonged operational lifetime and enhanced capability of moisture resistance are achieved simultaneously, approaching a half‐lifetime of ≈2900 s at an initial brightness of 178 cd m–2. [ABSTRACT FROM AUTHOR]

Regardless of the rapid advance on perovskite light‐emitting diodes (PeLEDs), the lack of long‐term operational stability hinders the practicality of this technology. Particularly, thermal management is indispensable to control the Joule heating induced by charge transport and parasitic re‐absorption of internally confined photons. Herein, a synergetic device architecture is proposed for minimizing the optical energy losses in PeLEDs toward high efficiency and long lifetime. By adopting a carefully modified perovskite emitter in combination with an improved light outcoupling structure, red PeLEDs emitting at 666 nm achieve a peak external quantum efficiency of 21.2% and an operational half‐lifetime of 4806.7 h for an initial luminance of 100 cd m‐2. The enhanced light extraction from trapped modes can efficiently reduce the driving current and suppress optical energy losses in PeLEDs, which in turn ameliorate the heat‐induced device degradation during operation. This work paves the way toward high‐performance PeLEDs for display and lighting applications in the future. [ABSTRACT FROM AUTHOR]

Metal halide perovskite light‐emitting diodes (PeLEDs) are gaining increasing attention as a promising candidate for the new‐generation display technology. Although tremendous progress has been witnessed in this field, the device performance of blue PeLEDs still lags far behind that of the green and red counterparts. In this work, an effective interfacial engineering is employed to boost the radiative recombination of blue perovskite film by introducing a multifunctional tetraethyl orthosilicate (TEOS) network on the grain‐growth substrate. Benefitting from the strong interaction between the TEOS molecule and perovskite nuclei, the perovskite crystallization dynamics are effectively regulated, contributing to significantly improved emitting film with uniformly distributed halogen and concentrated low‐dimensional domain. Additionally, the TEOS network can distinctly passivate the crystal defects at the buried perovskite interface owing to its adequate electron‐donating sites. Consequently, the target blue PeLEDs featuring a stable emission peak at 488 nm exhibit a champion external quantum efficiency of 17.3%, which is among the highest values to date. The results demonstrate the critical role of the surface molecular characteristics of the grain‐growth substrate in regulating the mixed‐halide blue perovskite crystallization. [ABSTRACT FROM AUTHOR]

Efficient and stable blue emission of perovskite light‐emitting diodes (PeLEDs) is a requisite toward their potential applications in full‐color displays and solid‐state lighting. Rational manipulation over the entire electroluminescence process is promising to break the efficiency limit of blue PeLEDs. Herein, a facile device architecture is proposed to achieve efficient blue PeLEDs for simultaneously reducing the energetic loss during electron‐photon conversion and boosting the light outcoupling. Effective interfacial engineering is employed to manipulate the perovskite crystallization nucleation, enabling highly compact perovskite nanocrystal assemblies and suppressing the trap‐induced carrier losses by means of interfacial hydrogen bonding interactions. This strategy contributes to a high external quantum efficiency (EQE) of 12.8% for blue PeLEDs emitting at 486 nm as well as improved operational stability. Moreover, blue PeLEDs reach a peak EQE of 16.8% with the incorporation of internal outcoupling structures for waveguided light, which can be further raised to 27.5% by integrating a lens‐based structure for substrate‐mode light. These results verify the validity of this strategy in producing efficient and stable blue PeLEDs for practical applications. [ABSTRACT FROM AUTHOR]

Perovskite light‐emitting diodes (PeLEDs) are emerging as promising candidates for new‐generation high‐definition displays with excellent color purity and low power consumption. Nevertheless, the massive defects at grain boundaries and severe interfacial exciton quenching are critical challenges that hinder the commercialization process of PeLEDs. Herein, a novel and feasible strategy of interfacial molecule control is demonstrated by employing a bifunctional material with abundant phosphine oxide groups to induce strong interaction and exciton management between the perovskite and electron‐transport layers (ETLs). This modification layer is capable of passivating the surface crystal defects and blocking the interfacial exciton transfer simultaneously, contributing to minimized energy loss at the interface. Consequently, the modified PeLEDs with green (at 513 nm), blue (at 488 nm), and red (at 666 nm) emissions achieve maximum external quantum efficiencies of 18.8%, 12.6%, and 12.3%, respectively. This study reveals the importance of interfacial molecule control for reducing the energy loss in PeLEDs. [ABSTRACT FROM AUTHOR]

Perovskite light‐emitting diodes (PeLEDs) are emerging candidates for the applications of solution‐processed full‐color displays. However, the device performance of deep‐blue PeLED still lags far behind that of their red and green counterparts, which is largely limited by low external quantum efficiency (EQE) and poor operational stability. Here, a facile and reliable crystallization strategy for perovskite grains is proposed, with improved deep‐blue emission through rational interfacial engineering. By modifying the substrate with potassium cation (K+) as the supplier of heterogeneous nucleation seeds, the interfacial K+‐guided grain growth is realized for well‐packed perovskite assemblies with high surface coverage and the controlled crystal orientation, leading to the enhanced radiative recombination and hole‐transport capabilities. Synergistical boost in device performance is achieved for deep‐blue PeLEDs emitting at 469 nm with a peak EQE of 4.14%, a maximum luminance of 451 cd m–2, and spectrally stable color coordinates of (0.125, 0.076) that matches well with the National Television System Committee (NTSC) standard blue. [ABSTRACT FROM AUTHOR]

As a promising family of semiconductor materials for high‐quality displays, quasi‐2D perovskites have gained a significant amount of attention in the field of light‐emitting diodes for their superior optoelectronic properties compared with their 3D counterparts. The intrinsic multiple‐quantum‐well characteristics induced by reducing the crystal dimensionality enable perovskite emitters to possess high photoluminescence quantum yield and good film morphology. It is demonstrated that the n‐value distribution of quasi‐2D perovskites, where n refers to the number of inorganic MX6 octahedron layers, has a strong impact on the electroluminescence efficiency and stability of perovskite light‐emitting diodes (PeLEDs). In this review, the crystal structure of quasi‐2D perovskites, the formation origin of different n‐value distributions, and their optoelectronic characteristics are first introduced. Then, the mainstream strategies for regulating the phase distribution of layered perovskites are systematically reviewed to suggest their great significance in boosting the performances of PeLEDs. Lastly, the current deficiencies and potentially valuable research directions of phase distribution management for efficient and stable quasi‐2D PeLEDs are provided. [ABSTRACT FROM AUTHOR]

Organic light‐emitting diodes (OLEDs) based on thermally activated delayed fluorescence (TADF) materials are promising for the realization of highly efficient emitters. However, severe efficiency roll‐off at high brightness still remains as a huge challenge for TADF‐based OLEDs. Herein, rod‐like orange‐red TADF emitters of 2BNCz‐PZ and 2BNtCz‐PZ with acceptor‐donor‐acceptor (A‐D‐A) configuration are developed by bearing dihydrophenazine donor and discoidal rigid boron, nitrogen‐contained polycyclic aromatic hydrocarbons acceptors. Both emitters exhibit hybrid long‐range/short‐range charge‐transfer excitation for small singlet‐triplet energy splitting, short delayed lifetime, and high photoluminescence quantum yield, leading to fast singlet radiation rate over 107 s−1 and fast reverse intersystem crossing rate over 106 s−1. Furthermore, a horizontal emitting dipole orientation factor over 90% is realized. The optimized orange‐red OLED based on 2BNtCz‐PZ presents a maximum external quantum efficiency (EQE) of 31.0% and a slight EQE roll‐off to 22.2% at 1 000 cd m−2 with emission peak over 600 nm. In addition, the single‐emitting layer white OLEDs achieve a maximum EQE of 30.6% due to the use of these orange‐red dopants with intense charge‐transfer absorption band. This work reveals the potential of the rod‐like A‐D‐A configuration for constructing highly efficient orange‐red TADF emitters with low‐efficiency roll‐off. [ABSTRACT FROM AUTHOR]

Perovskite Light‐emitting diodes (PeLEDs) have emerged as a promising technique for future high‐definition displays due to their outstanding electroluminescent characters. However, the development of blue PeLEDs toward practical applications is seriously hindered by their inferior performance, which mainly arises from the detrimental halide ionic behavior and thus severe nonradiative recombination in mixed‐halide blue perovskite materials. Herein, efficient sky‐blue PeLEDs featuring spectrally stable emission at 483 nm are realized by employing bifunctional passivators of Lewis‐base benzoic acid anions and alkali metal cations to simultaneously passivate the under‐coordinated lead atoms and suppress halide ion migration. A decent external quantum efficiency (EQE) of 16.58% and a maximum EQE of 18.65% are achieved, which is further boosted to 28.82% through the optical outcoupling enhancement. This work demonstrates unique insight into the generality and individuality of this category of benzoates and puts forward a feasible guidance in choosing appropriate additives for efficient perovskite materials. [ABSTRACT FROM AUTHOR]

Heating is a knotty factor contributing to device degradation of flexible organic solar cells (FOSCs), and thermal regulation plays a crucial role in the realization of long operational lifetime. Herein, a passive cooling strategy for stable FOSCs is proposed by boosting the optical‐thermal radiative transfer to reduce the insufficient thermal dissipation and the elevated temperature caused by irradiation‐induced heating, while retaining their flexibility and portability. A spectrally selective coupling structure consisting of subwavelength hemisphere pattern and distributed Bragg reflector is integrated into FOSCs to collectively enhance out‐coupling of infrared radiation and limit near‐infrared absorption‐induced heat generation, leading to a reduced heat power intensity of 292.5 W cm−2 and the decreased working temperature by 9.6 °C under outdoor sunlight irradiation. The D18:Y6:PC71BM‐based FOSCs achieve a power conversion efficiency of over 17% with a prolonged T80 lifetime as long as one year under real outdoor working conditions. These results represent a new opportunity for enhancing the operational stability of FOSCs. [ABSTRACT FROM AUTHOR]

Polarization‐sensitive photodetectors are gaining numerous attention since polarization detection is important in geological remote sensing, atmospheric monitoring, military recon, and medical examination. Among various reported photoactive materials for photodetectors, metal halide perovskites have outstanding advantages such as tunable band gaps, excellent optoelectronic properties, and easy fabrication. Moreover, the characteristics of crystal structure anisotropy and controllable growth orientation of perovskite crystals endow the perovskite photodetector with the ability to identify light polarization states. This review outlines the recent research progress of perovskite photodetectors on polarization‐sensitive detection. Firstly, key device parameters of polarization‐sensitive detection are introduced. Then, the recent progress of polarization‐sensitive perovskite detectors in the field of linear and circular polarization is reviewed according to the different principles of polarization response. Finally, the challenges of polarization‐sensitive perovskite photodetector are discussed. [ABSTRACT FROM AUTHOR]

White organic light-emitting diodes (OLEDs) hold great promise for applications in displays and lighting due to high efficiency and superior white color balance. However, further improvement in efficiency remains a continuous and urgent demand due to limited energy flow extraction. A powerful method for drastically releasing the trapped energy flow in conventional white OLEDs is demonstrated by implementing unique quasi-periodic subwavelength nanofunnel arrays (NFAs) via soft nanoimprinting lithography, which is ideal for enhancing light extraction without any spectral distortion or angular dependence. The resulting efficiency is over 2 times that of a conventional OLED used as a comparison. The external quantum efficiency and power efficiency are raised to 32.4% and 56.9 lm W−1, respectively. Besides, the substantial increase in efficiency over a broad bandwidth with angular color stability, the experimental proofs show that the NFA-based extraction structure affords the enticing capacity against scrubbing and the self-cleaning feature, which are critical to the commercial viability in practical applications. [ABSTRACT FROM AUTHOR]

Highly power-efficient white organic light-emitting diodes (OLEDs) are still challenging to make for applications in high-quality displays and general lighting due to optical confinement and energy loss during electron-photon conversion. Here, an efficient white OLED structure is shown that combines deterministic aperiodic nanostructures for broadband quasi-omnidirectional light extraction and a multilayer energy cascade structure for energy-efficient photon generation. The external quantum efficiency and power efficiency are raised to 54.6% and 123.4 lm W−1 at 1000 cd m−2. An extremely small roll-off in efficiency at high luminance is also obtained, yielding a striking value of 106.5 lm W−1 at 5000 cd m−2. In addition to a substantial increase in efficiency, this device structure simultaneously offers the superiority of angular color stability over the visible wavelength range compared to conventional OLEDs. It is anticipated that these findings could open up new opportunities to promote white OLEDs for commercial applications. [ABSTRACT FROM AUTHOR]

Using narrow bandgap nonfullerene acceptors (NFAs) can broaden the absorption spectrum of organic solar cells (OSCs) to the near‐infrared region. However, the simultaneously decreased extinction coefficient of the active layer at the blue region results in inevitable light escaping and energy loss. Herein, a blazed grating‐based device configuration consisting of a patterned rear electrode is employed to compensate for the low absorption of nonfullerene OSCs. Experimental results reveal that the normal incidence light, especially blue light, that bounces off the patterned rear electrode is concentrated in a large tilted angle and subsequently trapped in waveguide mode. Along with the excitation of surface plasmon polariton, the structured nonfullerene OSCs using a new‐designed PM6:M36 active layer obtain the broadband absorption enhancement with 1.5 times increase at the blue region. The optimized device achieves an 8.95% increase in photocurrent and a champion power conversion efficiency of approaching 18%, which is the highest reported value among all the devices based on A‐D‐A type NFAs. [ABSTRACT FROM AUTHOR]

Using narrow bandgap nonfullerene acceptors (NFAs) can broaden the absorption spectrum of organic solar cells (OSCs) to the near‐infrared region. However, the simultaneously decreased extinction coefficient of the active layer at the blue region results in inevitable light escaping and energy loss. Herein, a blazed grating‐based device configuration consisting of a patterned rear electrode is employed to compensate for the low absorption of nonfullerene OSCs. Experimental results reveal that the normal incidence light, especially blue light, that bounces off the patterned rear electrode is concentrated in a large tilted angle and subsequently trapped in waveguide mode. Along with the excitation of surface plasmon polariton, the structured nonfullerene OSCs using a new‐designed PM6:M36 active layer obtain the broadband absorption enhancement with 1.5 times increase at the blue region. The optimized device achieves an 8.95% increase in photocurrent and a champion power conversion efficiency of approaching 18%, which is the highest reported value among all the devices based on A‐D‐A type NFAs. [ABSTRACT FROM AUTHOR]

Blue emission, composition engineering, defect passivation, light extraction, perovskite light-emitting diodes Keywords: blue emission; composition engineering; defect passivation; light extraction; perovskite light-emitting diodes EN blue emission composition engineering defect passivation light extraction perovskite light-emitting diodes 1 1 1 11/02/21 20211103 NES 211103 B Blue PeLEDs b In article number 2103870, Yan-Qing Li, Jian-Xin Tang, and co-workers demonstrate a facile and effective device architecture for efficient sky-blue perovskite light-emitting diodes by simultaneously suppressing energetic loss during electron-photon conversion and enhancing light outcoupling, yielding a record external quantum efficiency of 27.5%. Interfacial Nucleation Seeding for Electroluminescent Manipulation in Blue Perovskite Light-Emitting Diodes (Adv. Funct. [Extracted from the article]

All‐inorganic CsPbI2Br perovskite has attracted great attention as an absorber for perovskite solar cells (PSCs) due to its excellent thermal and light resistance. However, its device performance is restricted by the large energy level offset between CsPbI2Br and the most commonly used hole‐transporting layer (HTL). Herein, multicarbazolyl‐substituted benzonitrile (4t‐5CzBn) is inserted into the interface between CsPbI2Br and HTL to form a uniform stepped (0.24 eV) interfacial energy level structure, which reduces the energy loss and boosts the hole extraction of CsPbI2Br PSCs. The incorporation of 4t‐5CzBn induces the increase in open‐circuit voltage and fill factor from 1.256 V and 74.5% to 1.335 V and 82.3%, respectively. The optimized device achieves a power conversion efficiency of 17.34%, which is among the highest reported values of CsPbI2Br PSCs. Besides the energy level tuning effect, the tert‐butyl groups in 4t‐5CzBn improve the moisture‐resistance of CsPbI2Br PSCs. The unencapsulated device maintains over 75% of its initial efficiency after 700 h storage in air. These results demonstrate that the rational tuned energy level step benefits the performance improvement of CsPbI2Br PSCs. [ABSTRACT FROM AUTHOR]

Deep-Blue Emission: Interfacial Potassium-Guided Grain Growth for Efficient Deep-Blue Perovskite Light-Emitting Diodes (Adv. Funct. Keywords: crystallization manipulation; deep-blue emission; interface engineering; perovskite light-emitting diodes EN crystallization manipulation deep-blue emission interface engineering perovskite light-emitting diodes 1 1 1 02/05/21 20210203 NES 210203 In article number 2006736, Yan-Qing Li, Jian-Xin Tang, and co-workers demonstrate a facile and reliable crystallization strategy for interfacial potassium-guided perovskite grain growth, leading to efficient deep-blue light-emitting diodes with an external quantum efficiency of 4.14% and stable color coordinates of (0.125, 0.076). Crystallization manipulation, deep-blue emission, interface engineering, perovskite light-emitting diodes. [Extracted from the article]

On page 2660, J. X. Tang and co‐workers demonstrate a powerful method for drastically releasing the trapped energy flow in conventional white organic light‐emitting diodes by implementing a unique quasi‐periodic subwavelength nanofunnel array via soft nanoimprinting litho‐graphy. Besides the substantial increase in efficiency over a broad bandwidth without any spectral distortion or angular dependence, this array affords an enticing capacity against scrubbing and the self‐cleaning feature, which are critical to the commercial viability in practical applications. [ABSTRACT FROM AUTHOR]

A universal strategy for highly power‐efficient white organic light‐emitting diodes is developed by Y.‐Q. Li, J.‐X. Tang, and colleagues on page 7249 by combining deterministic aperiodic nanostructures for broadband quasi‐omnidirectional light extraction and a multilayer energy cascade structure for energy‐efficient photon generation. A record efficiency exceeding 120 lm W−1 is achieved with an extremely small roll‐off in efficiency and superior angular color stability. [ABSTRACT FROM AUTHOR]