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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 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]

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]

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]

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]

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]

Perovskite light‐emitting diodes (PeLEDs) have garnered extraordinary attention in displaying field owing to their excellent luminescence properties. Although exogenous additives are extensively employed for optimizing PeLEDs, their comprehensive regulation including side effects still lacks in‐depth study. Here for the first time, it is demonstrated that the deprotonation degree of additives significantly influences the performance of blue PeLEDs. Benzenesulfonic acid (BSA) and ammonium benzenesulfonate (ABS) with similar molecular structures while distinctly different acid dissociation constants (pKa) are used for modifying blue perovskites. By comparison, high‐pKa ABS holds greater potential in boosting device performance, contributing to an improved peak external quantum efficiency of 18.8%. This discrepancy is ascribed to the fact that low‐pKa BSA is prone to induce prominent perovskite chlorine loss owing to its intense deprotonation, while high‐pKa ABS significantly suppresses chlorine vacancy formation. Meanwhile, the adsorption energy of organic spacer onto perovskite is greatly reduced due to the strong intermolecular hydrogen bonding with ABS, contributing to a concentrated phase arrangement for smooth exciton energy transfer. Additionally, ABS modification further suppresses trap‐mediated nonradiative recombination by coordinating with the undercoordinated lead (II) ions at grain boundaries. This work provides valuable guidelines for optimizing additive screening toward high‐performance blue PeLEDs. [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]