Metal halide perovskite light emitters Kim, Young-Hoon; Cho, Himchan; Lee, Tae-Woo
Proceedings of the National Academy of Sciences - PNAS,
10/2016, Letnik:
113, Številka:
42
Journal Article
Recenzirano
Odprti dostop
Twenty years after layer-type metal halide perovskites were successfully developed, 3D metal halide perovskites (shortly, perovskites) were recently rediscovered and are attracting multidisciplinary ...interest from physicists, chemists, and material engineers. Perovskites have a crystal structure composed of five atoms per unit cell (ABX₃) with cation A positioned at a corner, metal cation B at the center, and halide anion X at the center of six planes and unique optoelectronic properties determined by the crystal structure. Because of very narrow spectra (full width at half-maximum ≤20 nm), which are insensitive to the crystallite/grain/particle dimension and wide wavelength range (400 nm ≤ λ ≤ 780 nm), perovskites are expected to be promising high-color purity light emitters that overcome inherent problems of conventional organic and inorganic quantum dot emitters. Within the last 2 y, perovskites have already demonstrated their great potential in light-emitting diodes by showing high electroluminescence efficiency comparable to those of organic and quantum dot light-emitting diodes. This article reviews the progress of perovskite emitters in two directions of bulk perovskite polycrystalline films and perovskite nanoparticles, describes current challenges, and suggests future research directions for researchers to encourage them to collaborate and to make a synergetic effect in this rapidly emerging multidisciplinary field.
The distributed network of receptors, neurons, and synapses in the somatosensory system efficiently processes complex tactile information. We used flexible organic electronics to mimic the functions ...of a sensory nerve. Our artificial afferent nerve collects pressure information (1 to 80 kilopascals) from clusters of pressure sensors, converts the pressure information into action potentials (0 to 100 hertz) by using ring oscillators, and integrates the action potentials from multiple ring oscillators with a synaptic transistor. Biomimetic hierarchical structures can detect movement of an object, combine simultaneous pressure inputs, and distinguish braille characters. Furthermore, we connected our artificial afferent nerve to motor nerves to construct a hybrid bioelectronic reflex arc to actuate muscles. Our system has potential applications in neurorobotics and neuroprosthetics.
Previous reports suggested that cinnamaldehyde (CA), the bioactive ingredient in Cinnamomum cassia, can suppress tumor growth, migratory, and invasive abilities. However, the role and molecular ...mechanisms of CA in GC are not completely understood. In the present study, we found that CA-induced ER stress and cell death via the PERK-CHOP axis and Ca
release in GC cells. Inhibition of ER stress using specific-siRNA blocked CA-induced cell death. Interestingly, CA treatment resulted in autophagic cell death by inducing Beclin-1, ATG5, and LC3B expression and by inhibiting p62 expression whereas autophagy inhibition suppressed CA-induced cell death. We showed that CA induces the inhibition of G9a and the activation of LC3B. Moreover, CA inhibited G9a binding on Beclin-1 and LC3B promoter. Overall, these results suggested that CA regulates the PERK-CHOP signaling, and G9a inhibition activates autophagic cell death via ER stress in GC cells.
Highly efficient organic/inorganic hybrid perovskite light‐emitting diodes (PeLEDs) based on graphene anode are developed for the first time. Chemically inert graphene avoids quenching of excitons by ...diffused metal atom species from indium tin oxide. The flexible PeLEDs with graphene anode on plastic substrate show good bending stability; they provide an alternative and reliable flexible electrode for highly efficient flexible PeLEDs.
Ruddlesden–Popper phase (RP‐phase) perovskites that consist of 2D perovskite slabs interleaved with bulky organic ammonium (OA) are favorable for light‐emitting diodes (LEDs). The critical limitation ...of LED applications is that the insulating OA arranged in a preferred orientation limits charge transport. Therefore, the ideal solution is to achieve a randomly connected structure that can improve charge transport without hampering the confinement of the electron–hole pair. Here, a structurally modulated RP‐phase metal halide perovskite (MHP), (PEA)2(CH3NH3)m−1PbmBr3m+1 is introduced to make the randomly oriented RP‐phase unit and ensure good connection between them by applying modified nanocrystal pinning, which leads to an increase in the efficiency of perovskite LEDs (PeLEDs). The randomly connected RP‐phase MHP forces contact between inorganic layers and thereby yields efficient charge transport and radiative recombination. Combined with an optimal dimensionality, (PEA)2(CH3NH3)2Pb3Br10, the structurally modulated RP‐phase MHP exhibits increased photoluminescence quantum efficiency, from 0.35% to 30.3%, and their PeLEDs show a 2,018 times higher current efficiency (20.18 cd A−1) than in the 2D PeLED (0.01 cd A−1) and 673 times than in the 3D PeLED (0.03 cd A−1) using the same film formation process. This approach provides insight on how to solve the limitation of RP‐phase MHP for efficient PeLEDs.
Ruddlesden–Popper phase (RP‐phase) perovskites are promising materials for optoelectronic devices. Efficient RP‐phase perovskite light‐emitting diodes (PeLEDs) are developed by introducing a structurally modulated RP‐phase metal halide perovskite (MHP) emitter to increase the charge transport ability without hampering the confinement of the electron–hole pair. This approach provides insight on how to solve the limitation of RP‐phase MHP for efficient PeLEDs.
Metal halide perovskites are attracting a lot of attention as next-generation light-emitting materials owing to their excellent emission properties, with narrow band emission
. However, perovskite ...light-emitting diodes (PeLEDs), irrespective of their material type (polycrystals or nanocrystals), have not realized high luminance, high efficiency and long lifetime simultaneously, as they are influenced by intrinsic limitations related to the trade-off of properties between charge transport and confinement in each type of perovskite material
. Here, we report an ultra-bright, efficient and stable PeLED made of core/shell perovskite nanocrystals with a size of approximately 10 nm, obtained using a simple in situ reaction of benzylphosphonic acid (BPA) additive with three-dimensional (3D) polycrystalline perovskite films, without separate synthesis processes. During the reaction, large 3D crystals are split into nanocrystals and the BPA surrounds the nanocrystals, achieving strong carrier confinement. The BPA shell passivates the undercoordinated lead atoms by forming covalent bonds, and thereby greatly reduces the trap density while maintaining good charge-transport properties for the 3D perovskites. We demonstrate simultaneously efficient, bright and stable PeLEDs that have a maximum brightness of approximately 470,000 cd m
, maximum external quantum efficiency of 28.9% (average = 25.2 ± 1.6% over 40 devices), maximum current efficiency of 151 cd A
and half-lifetime of 520 h at 1,000 cd m
(estimated half-lifetime >30,000 h at 100 cd m
). Our work sheds light on the possibility that PeLEDs can be commercialized in the future display industry.
Organic-inorganic hybrid perovskites are emerging low-cost emitters with very high color purity, but their low luminescent efficiency is a critical drawback. We boosted the current efficiency (CE) of ...perovskite light-emitting diodes with a simple bilayer structure to 42.9 candela per ampere, similar to the CE of phosphorescent organic light-emitting diodes, with two modifications: We prevented the formation of metallic lead (Pb) atoms that cause strong exciton quenching through a small increase in methylammonium bromide (MABr) molar proportion, and we spatially confined the exciton in uniform MAPbBr₃ nanograins (average diameter = 99.7 nanometers) formed by a nanocrystal pinning process and concomitant reduction of exciton diffusion length to 67 nanometers. These changes caused substantial increases in steady-state photoluminescence intensity and efficiency of MAPbBr₃ nanograin layers.
Organometal halide perovskites are promising photo-absorption materials in solar cells due to their high extinction coefficient, broad light absorption range and excellent semiconducting properties. ...The highest power conversion efficiency (PCE) of perovskite solar cells (PrSCs) is now 20.1%. However, a high-temperature processed mesoscopic metal oxide (
e.g.
, TiO
2
) must be removed to realize flexible PrSCs on plastic substrates using low temperature processes. Although the planar heterojunction (PHJ) structure can be considered as the most appropriate structure for flexible PrSCs, they have shown lower PCEs than those with a mesoscopic metal oxide layer. Therefore, development of interfacial layers is essential for achieving highly efficient PHJ PrSCs, and necessary in fabrication of flexible PrSCs. This review article gives an overview of progress in PHJ PrSCs and the roles of interfacial layers in the device, and suggests a practical strategy to fabricate highly efficient and flexible PHJ PrSCs. We conclude with our technical suggestion and outlook for further research direction.
This review article gives an overview of progress in planar heterojunction perovskite solar cells and the roles of interfacial layers in the device, and suggests a practical strategy to fabricate highly efficient and flexible planar heterojunction perovskite solar cells.
Electron‐injecting interlayers (ILs) which are stable in air, inject electrons efficiently, block holes, and block quenching of excitons, are very important to realize efficient inverted polymer ...light‐emitting diodes (IPLEDs). Two air‐stable polymer electron‐injecting interlayers (ILs), branched polyethyleneimine (PEI) and polyethyleneimine ethoxylated (PEIE) for use in IPLEDs are introduced, and the roles of the ILs in IPLEDs comparing these with a conventional Cs2CO3 IL are elucidated. These polymer ILs can reduce the electron injection barrier between ZnO and emitting layer by decreasing the work function (WF) of underlying ZnO, thereby effectively facilitating electron injection into the emitting layer. WF of ZnO covered by PEI is found to be lower than that covered by PEIE due to higher N+/C ratio of PEI. Furthermore, they can block the quenching of excitons and increase the luminous efficiency of devices. Thus, IPLEDs with PEI IL of optimum thickness (8 nm) show current efficiency (13.5 cd A–1), which is dramatically higher than that of IPLEDs with a Cs2CO3 IL (8 cd A‐1).
Efficient and air‐stable inverted polymer‐light emitting diodes (IPLEDs) can be realized by using insulating polymer electron‐injecting interlayers (ILs), branched polyethyleneimine (PEI), and polyethyleneimine ethoxylated (PEIE), giving highest current efficiencies of 13.5 cd A‐1 and 12 cd A‐1, respectively. Polymer ILs can facilitate electron injection into emitting layer as well as block the exciton quenching.
This paper reports highly bright and efficient CsPbBr3 perovskite light‐emitting diodes (PeLEDs) fabricated by simple one‐step spin‐coating of uniform CsPbBr3 polycrystalline layers on a ...self‐organized buffer hole injection layer and stoichiometry‐controlled CsPbBr3 precursor solutions with an optimized concentration. The PeLEDs have maximum current efficiency of 5.39 cd A−1 and maximum luminance of 13752 cd m−2. This paper also investigates the origin of current hysteresis, which can be ascribed to migration of Br− anions. Temperature dependence of the electroluminescence (EL) spectrum is measured and the origins of decreased spectrum area, spectral blue‐shift, and linewidth broadening are analyzed systematically with the activation energies, and are related with Br− anion migration, thermal dissociation of excitons, thermal expansion, and electron–phonon interaction. This work provides simple ways to improve the efficiency and brightness of all‐inorganic polycrystalline PeLEDs and improves understanding of temperature‐dependent ion migration and EL properties in inorganic PeLEDs.
Efficient and bright CsPbBr3 perovskite light‐emitting diodes are achieved using a one‐step fabrication of uniform CsPbBr3 polycrystalline layers on a self‐organized buffer hole injection layer without synthesis of quantum dots. A study of the temperature dependence of current hysteresis and electroluminescence spectrum provides understanding of ion migration, nonradiative pathways, and electron–phonon interaction in the CsPbBr3 perovskite light‐emitting diodes.
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