Synergies of Electrochemical Metallization and Valance Change in All‐Inorganic Perovskite Quantum Dots for Resistive Switching

The in‐depth understanding of ions' generation and movement inside all‐inorganic perovskite quantum dots (CsPbBr₃ QDs), which may lead to a paradigm to break through the conventional von Neumann bottleneck, is strictly limited. Here, it is shown that formation and annihilation of metal conductive filaments and Br^? ion vacancy filaments driven by an external electric field and light irradiation can lead to pronounced resistive‐switching effects. Verified by field‐emission scanning electron microscopy as well as energy‐dispersive X‐ray spectroscopy analysis, the resistive switching behavior of CsPbBr₃ QD‐based photonic resistive random‐access memory (RRAM) is initiated by the electrochemical metallization and valance change. By coupling CsPbBr₃ QD‐based RRAM with a p‐channel transistor, the novel application of an RRAM–gate field‐effect transistor presenting analogous functions of flash memory is further demonstrated. These results may accelerate the technological deployment of all‐inorganic perovskite QD‐based photonic resistive memory for successful logic application.     

Epitaxial Growth of CsPbX3 (X = Cl,Br, I) Perovskite Quantum Dots via Surface Chemical Conversion of Cs2GeF6 Double Perovskites: A Novel Strategy for the Formation of Leadless Hybrid Perovskite Phosphors with Enhanced Stability

Lead halide perovskites (LHPs) have received increased attention owing to their intriguing optoelectronic and photonic properties. However, the toxicity of lead and the lack of long‐term stability are potential obstacles for the application of LHPs. Herein, the epitaxial synthesis of CsPbX₃ (X = Cl, Br, I) perovskite quantum dots (QDs) by surface chemical conversion of Cs₂GeF₆ double perovskites with PbX₂ (X = Cl, Br, I) is reported. The experimental results show that the surface of the Cs₂GeF₆ double perovskites is partially converted into CsPbX₃ perovskite QDs and forms a CsPbX₃/Cs₂GeF₆ hybrid structure. The theoretical calculations reveal that the CsPbBr₃ conversion proceeds at the Cs₂GeF₆ edge through sequential growth of multiple PbBr₆ ^4? layers. Through the conversion strategy, luminescent and color‐tunable CsPbX₃ QDs can be obtained, and these products present high stability against decomposition due to anchoring effects. Moreover, by partially converting red emissive Cs₂GeF₆:Mn⁴⁺ to green emissive CsPbBr₃, the CsPbBr₃/Cs₂GeF₆:Mn⁴⁺ hybrid can be employed as a low‐lead hybrid perovskite phosphor on blue LED chips to produce white light. The leadless CsPbX₃/Cs₂GeF₆ hybrid structure with stable photoluminescence opens new paths for the rational design of efficient emission phosphors and may stimulate the design of other functional CsPbX₃/Cs‐containing hybrid structures.     

Solution‐Grown CsPbBr3/Cs4PbBr6 Perovskite Nanocomposites: Toward Temperature‐Insensitive Optical Gain

With regards to developing miniaturized coherent light sources, the temperature‐insensitivity in gain spectrum and threshold is highly desirable. Quantum dots (QDs) are predicted to possess a temperature‐insensitive threshold by virtue of the separated electronic states; however, it is never observed in colloidal QDs due to the poor thermal stability. Besides, for the classical II–VI QDs, the gain profile generally redshifts with increasing temperature, plaguing the device chromaticity. Herein, this paper addresses the above two issues simultaneously by embedding ligands‐free CsPbBr₃ nanocrystals in a wider band gap Cs₄PbBr₆ matrix by solution‐phase synthesis. The unique electronic structures of CsPbBr₃ nanocrystals enable temperature‐insensitive gain spectrum while the lack of ligands and protection from Cs₄PbBr₆ matrix ensure the thermal stability and high temperature operation. Specifically, a color drift‐free stimulated emission irrespective of temperature change (20–150 °C) upon two‐photon pumping is presented and the characteristic temperature is determined to be as high as ≈260 K. The superior gain properties of the CsPbBr₃/Cs₄PbBr₆ perovskite nanocomposites are directly validated by a vertical cavity surface emitting laser operating at temperature as high as 100 °C. The results shed light on manipulating optical gain from the advantageous CsPbBr₃ nanocrystals and represent a significant step toward the temperature‐insensitive frequency‐upconverted lasers.     

Goethite Quantum Dots as Multifunctional Additives for Highly Efficient and Stable Perovskite Solar Cells

Minimization of defects and ion migration in organic–inorganic lead halide perovskite films is desirable for obtaining photovoltaic devices with high power conversion efficiency (PCE) and long‐term stability. However, achieving this target is still a challenge due to the lack of efficient multifunctional passivators. Herein, to address this issue, n‐type goethite (FeOOH) quantum dots (QDs) are introduced into the perovskite light‐absorption layer for achieving efficient and stable perovskite solar cells (PSCs). It is found that the iron, oxygen, and hydroxyl of FeOOH QDs can interact with iodine, lead, and methylamine, respectively. As a result, the crystallization kinetics process can be retarded, thereby resulting in high quality perovskite films with large grain size. Meanwhile, the trap states of perovskite can be effectively passivated via interaction with the under‐coordinated metal (Pb) cations, halide (I) anions on the perovskite crystal surface. Consequently, the PSCs with FeOOH QDs achieve a high efficiency close to 20% with negligible hysteresis. Most strikingly, the long‐term stability of PSCs is significantly enhanced. Furthermore, compared with the CH₃NH₃PbI₃‐based device, a higher PCE of 21.0% is achieved for the device assembled with a Cs_0.05FA_0.81MA_0.14PbBr_0.45I_2.55 perovskite layer.     

Ultrastable CsPbBr3 Perovskite Quantum Dot and Their Enhanced Amplified Spontaneous Emission by Surface Ligand Modification

The poor stability and aggregation problem of CsPbBr₃ quantum dots (QDs) in air are great challenges for their future practical application. Herein, a simple and effective ligand‐modification strategy is proposed by introducing 2‐hexyldecanoic acid (DA) with two short branched chains to replace oleic acid (OA) with long chains during the synthesis process. These two short branched chains not only maintain their colloidal stability but also contribute to efficient radiative recombination. The calculations show that CsPbBr₃ QDs with DA modification (CsPbBr₃‐DA QDs) have larger binding energy than CsPbBr₃ QDs with OA (CsPbBr₃‐OA QDs), resulting in significantly enhanced stability. Due to the strong binding energy between DA ligands and QDs, CsPbBr₃‐DA QDs exhibit no aggregation phenomenon even after stored in air for more than 70 d, and CsPbBr₃‐DA QDs films can maintain 94.3% of initial PL intensity after 28 d, while in CsPbBr₃‐OA QDs films occurs a rapid degradation of PL intensity. Besides, the enhanced amplified spontaneous emission (ASE) performance of CsPbBr₃‐DA QDs films has been demonstrated under both one‐ and two‐photon laser excitation. The ASE threshold of CsPbBr₃‐DA QDs films is reduced by more than 50% and their ASE photostability is also improved, in comparison to CsPbBr₃‐OA QDs films.     

Low‐Voltage Photodetectors with High Responsivity Based on Solution‐Processed Micrometer‐Scale All‐Inorganic Perovskite Nanoplatelets

All‐inorganic photodetectors based on scattered CsPbBr₃ nanoplatelets with lateral dimension as large as 10 µm are fabricated, and the CsPbBr₃ nanoplatelets are solution processed governed by a newly developed ion‐exchange soldering mechanism. Under illumination of a 442 nm laser, the photoresponsivity of photodetectors based on these scattered CsPbBr₃ nanoplatelets is as high as 34 A W^?1, which is the largest value reported from all‐inorganic perovskite photodetectors with an external driven voltage as small as 1.5 V. Moreover, the rise and fall times are 0.6 and 0.9 ms, respectively, which are comparable to most of the state‐of‐the‐art all‐inorganic perovskite‐based photodetectors. All the material synthesis and device characterization are conducted at room temperature in ambient air. This work demonstrates that the solution‐processed large CsPbBr₃ nanoplatelets are attractive candidates to be applied in low‐voltage, low‐cost, ultra highly integrated optoelectronic devices.     

Slow‐Photon‐Effect‐Induced Photoelectrical‐Conversion Efficiency Enhancement for Carbon‐Quantum‐Dot‐Sensitized Inorganic CsPbBr3 Inverse Opal Perovskite Solar Cells

All‐inorganic cesium lead halide perovskite is suggested as a promising candidate for perovskite solar cells due to its prominent thermal stability and comparable light absorption ability. Designing textured perovskite films rather than using planar‐architectural perovskites can indeed optimize the optical and photoelectrical conversion performance of perovskite photovoltaics. Herein, for the first time, this study demonstrates a rational strategy for fabricating carbon quantum dot (CQD‐) sensitized all‐inorganic CsPbBr₃ perovskite inverse opal (IO) films via a template‐assisted, spin‐coating method. CsPbBr₃ IO introduces slow‐photon effect from tunable photonic band gaps, displaying novel optical response property visible to naked eyes, while CQD inlaid among the IO frameworks not only broadens the light absorption range but also improves the charge transfer process. Applied in the perovskite solar cells, compared with planar CsPbBr₃, slow‐photon effect of CsPbBr₃ IO greatly enhances the light utilization, while CQD effectively facilitates the electron–hole extraction and injection process, prolongs the carrier lifetime, jointly contributing to a double‐boosted power conversion efficiency (PCE) of 8.29% and an increased incident photon‐to‐electron conversion efficiency of up to 76.9%. The present strategy on CsPbBr₃ IO to enhance perovskite PCE can be extended to rationally design other novel optoelectronic devices.     

Substantially Improving Device Performance of All‐Inorganic Perovskite‐Based Phototransistors via Indium Tin Oxide Nanowire Incorporation

All‐inorganic halide perovskites (IHPs) have attracted enormous attention due to their intrinsically high optical absorption coefficient and superior ambient stabilities. However, the photosensitivity of IHP‐based photodetectors is still restricted by their poor conductivities. Here, a facile design of hybrid phototransistors based on the CsPbBr₃ thin film and indium tin oxide (ITO) nanowires (NWs) integrated into a InGaZnO channel in order to achieve both high photoresponsivity and fast response is reported. The metallic ITO NWs are employed as electron pumps and expressways to efficiently extract photocarriers from CsPbBr₃ and inject electrons into InGaZnO. The obtained device exhibits the outstanding responsivity of 4.9 × 10⁶ A W^?1, which is about 100‐fold better than the previous best results of CsPbBr₃‐based photodetectors, together with the fast response (0.45/0.55 s), long‐term stability (200 h in ambient), and excellent mechanical flexibility. By operating the phototransistor in the depletion regime, an ultrahigh specific detectivity up to 7.6 × 10¹³ Jones is achieved. More importantly, the optimized spin‐coating manufacturing process is highly beneficial for achieving uniform InGaZnO‐ITO/perovskite hybrid films for high‐performance flexible detector arrays. All these results can not only indicate the potential of these hybrid phototransistors but also provide a valuable insight into the design of hybrid material systems for high‐performance photodetection.     

Aqueous Phase Exfoliating Quasi‐2D CsPbBr3 Nanosheets with Ultrahigh Intrinsic Water Stability

All‐inorganic cesium lead halide perovskite nanocrystals (NCs) have emerged as attractive optoelectronic materials due to the excellent optical and electronic properties. However, their environmental stability, especially in the presence of water, is still a significant challenge for their further commercialization. Here, ultrahigh intrinsically water‐stable all‐inorganic quasi‐2D CsPbBr₃ nanosheets (NSs) via aqueous phase exfoliation method are reported. Compared to conventional perovskite NCs, these unique quasi‐2D CsPbBr₃ nanosheets present an outstanding long‐term water stability with 87% photoluminescence (PL) intensity remaining after 168 h under water conditions. Moreover, the photoluminescence quantum yields (PLQY) of quasi‐2D CsPbBr₃ NSs is up to 82.3%, and these quasi‐2D CsPbBr₃ NSs also present good photostability of keeping 85% PL intensity after 2 h under 365 nm UV light. Evidently, such quasi‐2D perovskite NSs will open up a new way to investigate the intrinsic stability of all‐inorganic perovskites and further promote the commercial development of perovskite‐based optoelectronic and photovoltaic devices.     

Room‐Temperature Triple‐Ligand Surface Engineering Synergistically Boosts Ink Stability,Recombination Dynamics,and Charge Injection toward EQE‐11.6% Perovskite QLEDs

Developing low‐cost and high‐quality quantum dots (QDs) or nanocrystals (NCs) and their corresponding efficient light‐emitting diodes (LEDs) is crucial for the next‐generation ultra‐high‐definition flexible displays. Here, there is a report on a room‐temperature triple‐ligand surface engineering strategy to play the synergistic role of short ligands of tetraoctylammonium bromide (TOAB), didodecyldimethylammonium bromide (DDAB), and octanoic acid (OTAc) toward “ideal” perovskite QDs with a high photoluminescence quantum yield (PLQY) of >90%, unity radiative decay in its intrinsic channel, stable ink characteristics, and effective charge injection and transportation in QD films, resulting in the highly efficient QD‐based LEDs (QLEDs). Furthermore, the QD films with less nonradiative recombination centers exhibit improved PL properties with a PLQY of 61% through dopant engineering in A‐site. The robustness of such properties is demonstrated by the fabrication of green electroluminescent LEDs based on CsPbBr₃ QDs with the peak external quantum efficiency (EQE) of 11.6%, and the corresponding peak internal quantum efficiency (IQE) and power efficiency are 52.2% and 44.65 lm W^?1, respectively, which are the most‐efficient perovskite QLEDs with colloidal CsPbBr₃ QDs as emitters up to now. These results demonstrate that the as‐obtained QD inks have a wide range application in future high‐definition QD displays and high‐quality lightings.     

Ultrathin,Core–Shell Structured SiO2 Coated Mn2+‐Doped Perovskite Quantum Dots for Bright White Light‐Emitting Diodes

All‐inorganic semiconductor perovskite quantum dots (QDs) with outstanding optoelectronic properties have already been extensively investigated and implemented in various applications. However, great challenges exist for the fabrication of nanodevices including toxicity, fast anion‐exchange reactions, and unsatisfactory stability. Here, the ultrathin, core–shell structured SiO₂ coated Mn²⁺ doped CsPbX₃ (X = Br, Cl) QDs are prepared via one facile reverse microemulsion method at room temperature. By incorporation of a multibranched capping ligand of trioctylphosphine oxide, it is found that the breakage of the CsPbMnX₃ core QDs contributed from the hydrolysis of silane could be effectively blocked. The thickness of silica shell can be well‐controlled within 2 nm, which gives the CsPbMnX₃@SiO₂ QDs a high quantum yield of 50.5% and improves thermostability and water resistance. Moreover, the mixture of CsPbBr₃ QDs with green emission and CsPbMnX₃@SiO₂ QDs with yellow emission presents no ion exchange effect and provides white light emission. As a result, a white light‐emitting diode (LED) is successfully prepared by the combination of a blue on‐chip LED device and the above perovskite mixture. The as‐prepared white LED displays a high luminous efficiency of 68.4 lm W^?1 and a high color‐rendering index of Ra = 91, demonstrating their broad future applications in solid‐state lighting fields.     

Atomic‐Layer Deposition‐Assisted Double‐Side Interfacial Engineering for High‐Performance Flexible and Stable CsPbBr3 Perovskite Photodetectors toward Visible Light Communication Applications

Self‐powered photodetectors (PDs) based on inorganic metal halide perovskites are regarded as promising alternatives for the next generation of photodetectors. However, uncontrollable film growth and sluggish charge extraction at interfaces directly limit the sensitivity and response speed of perovskite‐based photodetectors. Herein, by assistance of an atomic layer deposition (ALD) technique, CsPbBr₃ perovskite thin films with preferred orientation and enlarged grain size are obtained on predeposited interfacial modification layers. Thanks to improved film quality and double side interfacial engineering, the optimized CsPbBr₃ (Al₂O₃/CsPbBr₃/TiO₂, ACT) perovskite PDs exhibit outstanding performance with ultralow dark current of 10^?11 A, high detectivity of 1.88 × 10¹³ Jones and broad linear dynamic range (LDR) of 172.7 dB. Significantly, excellent long‐term environmental stability (ambient conditions >100 d) and flexibility stability (>3000 cycles) are also achieved. The remarkable performance is credited to the synergistic effects of high carrier conductivity and collection efficiency, which is assisted by ALD modification layers. Finally, the ACT PDs are successfully integrated into a visible light communication system as a light receiver on transmitting texts, showing a bit rate as high as 100 kbps. These results open the window of high performance all‐inorganic halide perovskite photodetectors and extends to rational applications for optical communication.     

Low‐Saturation‐Intensity,High‐Photostability,and High‐Resolution STED Nanoscopy Assisted by CsPbBr3 Quantum Dots

Stimulated emission depletion (STED) nanoscopy is one of the most promising super‐resolution imaging techniques for microstructure imaging. Commercial CdSe@ZnS quantum dots are used as STED probes and ≈50 nm lateral resolution is obtained. Compared with other quantum dots, perovskite CsPbBr₃ nanoparticles (NPs) possess higher photoluminescence quantum yield and larger absorption cross‐section, making them a more effective probe for STED nanoscopy. In this study, CsPbBr₃ NPs are used as probes for STED nanoscopy imaging. The fluorescence intensity of the CsPbBr₃ sample is hardly weakened at all after 200 min irradiation with a 39.8 mW depletion laser, indicating excellent photobleaching resistance of the CsPbBr₃ NPs. The saturation intensity of the CsPbBr₃ NPs is extremely low and estimated to be only 0.4 mW (0.126 MW cm^?2). Finally, an ultrahigh lateral resolution of 20.6 nm is obtained for a single nanoparticle under 27.5 mW STED laser irradiation in CsPbBr₃‐based STED nanoscopy imaging, which is a tenfold improvement compared with confocal microscopy. Because of its high fluorescence stability and ultrahigh resolution under lower depletion power, CsPbBr₃‐assisted STED nanoscopy has great potential to investigate microstructures that require super‐resolution and long‐term imaging.     

A Semitransparent Inorganic Perovskite Film for Overcoming Ultraviolet Light Instability of Organic Solar Cells and Achieving 14.03% Efficiency

Organic solar cells (OSCs) can be unstable under ultraviolet (UV) irradiation. To address this issue and enhance the power conversion efficiency (PCE), an inorganic‐perovskite/organic four‐terminal tandem solar cell (TSC) based on a semitransparent inorganic CsPbBr₃ perovskite solar cell (pero‐SC) as the top cell and an OSC as bottom cell is constructed. The high‐quality CsPbBr₃ photoactive layer of the planar pero‐SC is prepared with a dual‐source vacuum coevaporation method, using stoichiometric precursors of CsBr and PbBr₂ with a low evaporation rate. The resultant opaque planar pero‐SC exhibits an ultrahigh open‐circuit voltage of 1.44 V and the highest reported PCE of 7.78% for a CsPbBr₃‐based planar pero‐SC. Importantly, the devices show no degradation after 120 h UV light illumination. The related semitransparent pero‐SC can almost completely filter UV light and well maintain photovoltaic performance; it additionally shows an extremely high average visible transmittance. When it is used to construct a TSC, the top pero‐SC acting as a UV filter can utilize UV light for photoelectric conversion, avoiding the instability problem of UV light on the bottom OSC that can meet the industrial standards of UV‐light stability for solar cells, and leading to the highest reported PCE of 14.03% for the inorganic‐perovskite/organic TSC.     

Flexible and Self-Powered Photodetector Arrays Based on All-Inorganic CsPbBr3 Quantum Dots

Flexible devices are garnering substantial interest owing to their potential for wearable and portable applications. Here, flexible and self-powered photodetector arrays based on all-inorganic perovskite quantum dots (QDs) are reported. CsBr/KBr-mediated CsPbBr₃ QDs possess improved surface morphology and crystallinity with reduced defect densities, in comparison with the pristine ones. Systematic material characterizations reveal enhanced carrier transport, photoluminescence efficiency, and carrier lifetime of the CsBr/KBr-mediated CsPbBr₃ QDs. Flexible photodetector arrays fabricated with an optimum CsBr/KBr treatment demonstrate a high open-circuit voltage of 1.3 V, responsivity of 10.1 A W⁻¹, specific detectivity of 9.35 × 10¹³ Jones, and on/off ratio up to ≈10⁴. Particularly, such performance is achieved under the self-powered operation mode. Furthermore, outstanding flexibility and electrical stability with negligible degradation after 1600 bending cycles (up to 60°) are demonstrated. More importantly, the flexible detector arrays exhibit uniform photoresponse distribution, which is of much significance for practical imaging systems, and thus promotes the practical deployment of perovskite products.     

Dynamic Passivation in Perovskite Quantum Dots for Specific Ammonia Detection at Room Temperature

Perovskite structured CsPbX₃ (X = Cl, Br, or I) quantum dots (QDs) have attracted considerable interest in the past few years due to their excellent optoelectronic properties. Surface passivation is one of the main pathways to optimize the optoelectrical performance of perovskite QDs, in which the amino group plays an important role for the corresponding interaction between lead and halide. In this work, it is found that ammonia gas could dramatically increase photoluminescence of purified QDs and effectively passivate surface defects of perovskite QDs introduced during purification, which is a reversible process. This phenomenon makes perovskite QDs a kind of ideal candidate for detection of ammonia gas at room temperature. This QD film sensor displays specific recognition behavior toward ammonia gas due to its significant fluorescence enhancement, while depressed luminescence in case of other gases. The sensor, in turn‐on mode, shows a wide detection range from 25 to 350 ppm with a limit of detection as low as 8.85 ppm. Meanwhile, a fast response time of ≈10 s is achieved, and the recovery time is ≈30 s. The fully reversible, high sensitivity and selectivity characteristics make CsPbBr₃ QDs ideal active materials for room‐temperature ammonia sensing.     

Dual‐Phase CsPbBr3–CsPb2Br5 Perovskite Thin Films via Vapor Deposition for High‐Performance Rigid and Flexible Photodetectors

Inorganic perovskites with special semiconducting properties and structures have attracted great attention and are regarded as next generation candidates for optoelectronic devices. Herein, using a physical vapor deposition process with a controlled excess of PbBr₂, dual‐phase all‐inorganic perovskite composite CsPbBr₃–CsPb₂Br₅ thin films are prepared as light‐harvesting layers and incorporated in a photodetector (PD). The PD has a high responsivity and detectivity of 0.375 A W^?1 and 10¹¹ Jones, respectively, and a fast response time (from 10% to 90% of the maximum photocurrent) of ≈280 µs/640 µs. The device also shows an excellent stability in air for more than 65 d without encapsulation. Tetragonal CsPb₂Br₅ provides satisfactory passivation to reduce the recombination of the charge carriers, and with its lower free energy, it enhances the stability of the inorganic perovskite devices. Remarkably, the same inorganic perovskite photodetector is also highly flexible and exhibits an exceptional bending performance (>1000 cycles). These results highlight the great potential of dual‐phase inorganic perovskite films in the development of optoelectronic devices, especially for flexible device applications.     

Electric-Field-Regulated Energy Transfer in Chiral Liquid Crystals for Enhancing Upconverted Circularly Polarized Luminescence through Steering the Photonic Bandgap

Circularly polarized luminescent materials with high dissymmetry factor (g_lum) have been attracting increasing attention due to their distinctive photonic properties. In this work, by incorporating upconversion nanoparticles (UCNPs) and CsPbBr₃ perovskite nanocrystals (PKNCs) into a chiral nematic liquid crystal (N*LC), enhanced upconverted circularly polarized luminescence (UC-CPL) based on a radiative energy transfer (RET) process from UCNPs to CsPbBr₃ PKNCs is successfully implemented. By locating the emission peak of CsPbBr₃ PKNCs at the center of the photonic bandgap of N*LC, the maximum g_lum value of UC-CPL can be amplified to an extremely large value of 1.1. Meanwhile, upconverted emission of UCNPs can be significantly enhanced due to the band edge enhancement effect of the N*LC, subsequently enhancing the emission of the CsPbBr₃ PKNCs through the RET process. In addition, an applied electric field can switch the upconverted emission of the UCNPs, as well as the RET process, enabling an electric-field-controlled UC-CPL switch.     

A Strategy for Architecture Design of Crystalline Perovskite Light‐Emitting Diodes with High Performance

All present designs of perovskite light‐emitting diodes (PeLEDs) stem from polymer light‐emitting diodes (PLEDs) or perovskite solar cells. The optimal structure of PeLEDs can be predicted to differ from PLEDs due to the different fluorescence dynamics and crystallization between perovskite and polymer. Herein, a new design strategy and conception is introduced, “insulator–perovskite–insulator” (IPI) architecture tailored to PeLEDs. As examples of FAPbBr₃ and MAPbBr₃, it is experimentally shown that the IPI structure effectively induces charge carriers into perovskite crystals, blocks leakage currents via pinholes in the perovskite film, and avoids exciton quenching simultaneously. Consequently, as for FAPbBr₃, a 30‐fold enhancement in the current efficiency of IPI‐structured PeLEDs compared to a control device with poly(3,4ethylenedioxythiophene):poly(styrene sulfonate) as hole‐injection layer is achieved—from 0.64 to 20.3 cd A^?1—while the external quantum efficiency is increased from 0.174% to 5.53%. As the example of CsPbBr₃, compared with the control device, both current efficiency and lifetime of IPI‐structured PeLEDs are improved from 1.42 and 4 h to 9.86 cd A^?1 and 96 h. This IPI architecture represents a novel strategy for the design of light‐emitting didoes based on various perovskites with high efficiencies and stabilities.     

Imbedded Nanocrystals of CsPbBr3 in Cs4PbBr6: Kinetics,Enhanced Oscillator Strength,and Application in Light‐Emitting Diodes

Solution‐grown films of CsPbBr₃ nanocrystals imbedded in Cs₄PbBr₆ are incorporated as the recombination layer in light‐emitting diode (LED) structures. The kinetics at high carrier density of pure (extended) CsPbBr₃ and the nanoinclusion composite are measured and analyzed, indicating second‐order kinetics in extended and mainly first‐order kinetics in the confined CsPbBr₃, respectively. Analysis of absorption strength of this all‐perovskite, all‐inorganic imbedded nanocrystal composite relative to pure CsPbBr₃ indicates enhanced oscillator strength consistent with earlier published attribution of the sub‐nanosecond exciton radiative lifetime in nanoprecipitates of CsPbBr₃ in melt‐grown CsBr host crystals and CsPbBr₃ evaporated films.