High-Performing Quasi-2D Perovskite Photodetectors with Efficient Charge Transport Network Built from Vertically Orientated and Evenly Distributed 3D-Like Phases

Quasi-two-dimensional (Q-2D) perovskites are emerging as one of the most promising materials for photodetectors. However, a significant challenge to Q-2D perovskites for photodetection is their insufficient charge transport ability, which is mainly attributed to their hybrid low-dimensional n-phase structure. This study demonstrates that evenly-distributed 3D-like phases with vertical orientation throughout the film can greatly facilitate charge transport and suppress charge recombination, outperforming the prevalent phase structure with a vertical dimension gradient. Based on such a phase structure, a Q-2D Ruddlesden−Popper perovskite self-powered photodetector achieving a combination of exceptional figures-of-merit is realized, including a responsivity of 0.45 AW⁻¹, a peak specific detectivity of 2.3 × 10¹³ Jones, a 156 dB linear dynamic range, and a rise/fall time of 2.89 µs/1.93 µs. The desired phase structure is obtained by utilizing a double-hole transport layer (HTL), combining hydrophobic PTAA and hydrophilic PEDOT: PSS. Besides, the dependence of the hybrid low-dimensional phase structure is also identified on the surface energy of the buried HTL substrate. This study gives insight into the correlation between Q-2D perovskites’ phase structure and performance, providing a valuable design guide for Q-2D perovskite-based photodetectors.     

Highly Sensitive Self-Powered 2D Perovskite Photodiodes with Dual Interface Passivations

2D perovskites have attracted intensive attention by virtue of their excellent optical and electrical properties along with good stabilities. Herein, a highly sensitive self-powered photodiode based on (PEA)₂(MA)₄Pb₅I₁₆ (PEA=C₆H₅(CH₂)NH₃, MA=CH₃NH₃) 2D perovskite is demonstrated by dual interface passivations. The Al₂O₃ bottom passivation can reduce the pinhole defects in the 2D perovskite film and suppress the trap-related recombination loss, bringing forward much reduced dark current and increased photocurrent. The poly (methyl methacrylate) (PMMA) top passivation can encapsulate the 2D perovskite film and thus improve the stability of the device. These results show that the 2D perovskite-based photodiode with dual interface passivations exhibits a large photo-to-dark current ratio of 10⁷, a fast response speed of 597 ns and a linear dynamic range of 160 dB without bias. Responsivity (R) and detectivity (D*) respectively reach 0.36 A W⁻¹ and 5.4 × 10¹² Jones under 532 nm laser illumination at a power density of 1.5 nW cm⁻². Moreover, the dual interface passivated device exhibits good stabilities. This study paves the road for developing low-cost, low-power, solution processed image sensors.     

Flexible and Self‐Powered Lateral Photodetector Based on Inorganic Perovskite CsPbI3–CsPbBr3 Heterojunction Nanowire Array

Self‐powered perovskite photodetectors mainly adopt the vertical heterojunction structure composed of active layer, electron–hole transfer layers, and electrodes, which results in the loss of incident light and interfacial accumulation of defects. To address these issues, a self‐powered lateral photodetector based on CsPbI₃–CsPbBr₃ heterojunction nanowire arrays is designed on both a rigid glass and a flexible polyethylene naphthalate substrate using an in situ conversion and mask‐assisted electrode fabrication method. Through adding the polyvinyl pyrrolidone and optimizing the concentration of precursors under the pressure‐assisted moulding process, both the crystallinity and stability of perovskite nanowire array are improved. The nanowire array–based lateral device shows a high responsivity of 125 mA W^?1 and a fast rise and decay time of 0.7 and 0.8 ms under a self‐powered operation condition. This work provides a new strategy to fabricate perovskite heterojunction nanoarrays towards self‐powered photodetection.     

All-Inorganic CsPbBr3 Perovskite Nanocrystals/2D Non-Layered Cadmium Sulfide Selenide for High-Performance Photodetectors by Energy Band Alignment Engineering

Perovskites have attracted intensive attention as promising materials for the application in various optoelectronic devices due to their large light absorption coefficient, high carrier mobility, and long charge carrier diffusion length. However, the performance of the pure perovskite nanocrystals-based device is extremely restricted by the limited charge transport capability due to the existence of a large number of the grain boundary between perovskite nanocrystals. To address these issues, a high-performance photodetector based on all-inorganic CsPbBr₃ perovskite nanocrystals/2D non-layered cadmium sulfide selenide heterostructure has been demonstrated through energy band engineering with designed typed-II heterostructure. The photodetector exhibits an ultra-high light-to-dark current ratio of 1.36 × 10⁵, a high responsivity of 2.89 × 10² A W⁻¹, a large detectivity of 1.28 × 10¹⁴ Jones, and the response/recovery time of 0.53s/0.62 s. The enhancement of the optoelectronic performance of the heterostructure photodetector is mainly attributed to the efficient charge carrier transfer ability between the all-inorganic CsPbBr₃ perovskites and 2D cadmium sulfide selenide resulting from energy band alignment engineering. The charge carriers’ transfer dynamics and the mechanism of the CsPbBr₃ perovskites/2D non-layered nanosheets interfaces have also been studied by state-state PL spectra, fluorescence lifetime imaging microscopy, time-resolved photoluminescence spectroscopy, and Kelvin probe force microscopy measurements.     

Air-Stable Self-Powered Photodetectors Based on Lead-Free CsBi3I10/SnO2 Heterojunction for Weak Light Detection

Lead halide perovskites (LHPs) have been widely investigated in photodetection applications owing to their intriguing optoelectronic properties. However, the application of LHPs-based photodetectors (PDs) is hindered because of the toxicity of lead and instability in ambient air. Here, an air-stable self-powered photodetector is designed based on all-inorganic lead-free CsBi₃I₁₀/SnO₂ heterojunction. The device exhibits broad spectral response in both UV and visible light, fast response on µs scale, and decent long-term stability. The device holds a faster response speed (t_r/t_d = 7.8/8.8 µs), among the best reported self-powered lead-free perovskites photodetectors. More importantly, the device can display obvious photoresponses even under ultra-weak light intensity as low as 10 pW cm^–2, showing better weak-light sensitivity than previously reported lead-free perovskites photodetectors, to the best of our knowledge. Moreover, the device holds good air stability in the 73 days test without encapsulation. These results suggest that CsBi₃I₁₀/SnO₂-based self-powered PDs with high photodetection capability possess enormous potential in stable and broadband PDs for weak light detection in the future.     

Ultrahigh Stability 3D TI Bi2Se3/MoO3 Thin Film Heterojunction Infrared Photodetector at Optical Communication Waveband

Infrared (IR) detection at 1300–1650 nm (optical communication waveband) is of great significance due to its wide range of applications in commerce and military. Three dimensional (3D) topological insulator (TI) Bi₂Se₃ is considered a promising candidate toward high‐performance IR applications. Nevertheless, the IR devices based on Bi₂Se₃ thin films are rarely reported. Here, a 3D TI Bi₂Se₃/MoO₃ thin film heterojunction photodetector is shown that possesses ultrahigh responsivity (R_i), external quantum efficiency (EQE), and detectivity (D*) in the broadband spectrum (405–1550 nm). The highest on–off ratio of the optimized device can reach up to 5.32 × 10⁴. R_i, D*, and the EQE can reach 1.6 × 10⁴ A W^?1, 5.79 × 10¹¹ cm² Hz^1/2 W^?1, and 4.9 × 10⁴% (@ 405 nm), respectively. Surprisingly, the R_i can achieve 2.61 × 10³ A W^?1 at an optical communication wavelength (@ 1310 nm) with a fast response time (63 µs), which is two orders of magnitude faster than that of other TIs‐based devices. In addition, the device demonstrates brilliant long‐term (>100 days) environmental stability under environmental conditions without any protective measures. Excellent device photoelectric properties illustrate that the 3D TI/inorganic heterojunction is an appropriate way for manufacturing high‐performance photodetectors in the optical communication, military, and imaging fields.     

Mixed‐Dimensional 1D ZnO–2D WSe2 van der Waals Heterojunction Device for Photosensors

2D layered van der Waals (vdW) atomic crystals are an emerging class of new materials that are receiving increasing attention owing to their unique properties. In particular, the dangling‐bond‐free surface of 2D materials enables integration of differently dimensioned materials into mixed‐dimensional vdW heterostructures. Such mixed‐dimensional heterostructures herald new opportunities for conducting fundamental nanoscience studies and developing nanoscale electronic/optoelectronic applications. This study presents a 1D ZnO nanowire (n‐type)–2D WSe₂ nanosheet (p‐type) vdW heterojunction diode for photodetection and imaging process. After amorphous fluoropolymer passivation, the ZnO–WSe₂ diode shows superior performance with a much‐enhanced rectification (ON/OFF) ratio of over 10⁶ and an ideality factor of 3.4–3.6 due to the carbon–fluorine (C? F) dipole effect. This heterojunction device exhibits spectral photoresponses from ultraviolet (400 nm) to near infrared (950 nm). Furthermore, a prototype visible imager is demonstrated using the ZnO–WSe₂ heterojunction diode as an imaging pixel. To the best of our knowledge, this is the first demonstration of an optoelectronic device based on a 1D–2D hybrid vdW heterojunction. This approach using a 1D ZnO–2D WSe₂ heterojunction paves the way for the further development of electronic/optoelectronic applications using mixed‐dimensional vdW heterostructures.     

Domain Controlling by Compound Additive toward Highly Efficient Quasi-2D Perovskite Light-Emitting Diodes

Quasi-2D perovskites with enlarged exciton binding energy and tunable bandgap are appealing for application in perovskite light-emitting diodes (PeLEDs). However, wide n domains distribution is commonly formed in solution-processed quasi-2D perovskite films due to the uncontrollable crystallization behavior, which leads to low device performance. Here, the crystallization process is successfully regulated to narrow the n domains distribution by introducing compound additive of ZrO₂ nanoparticles (NPs) and Cryptand complexant. ZrO₂ NPs can avoid the segregation of organic large and small cations by strengthening the solvent extraction capacity of antisolvent, while Cryptand offsets the poor solubility of PbBr₂ by forming an intermediate state to slow down the crystallization of high-n domains. Consequently, both high photoluminescence quantum yields over 90% and a high external quantum efficiency of 21.2% are obtained in the optimized green quasi-2D PeLEDs. Moreover, the lifetime extends about four times compared with control devices. The strategy of domain controlling by compound additive provides a powerful way to develop high-performance quasi-2D perovskite optoelectrical devices.     

Functional 2D Phases in Mixed Dimensional Perovskite Photovoltaics

Organic-inorganic hybrid perovskite solar cells (PSCs) with unique properties exhibit their powerful competitiveness in the photovoltaic field over the past few years. However, the challenges of stability for perovskite devices limit the commercialization and further development. The 2D/3D hybrid structures combine the superior efficiency of bulk perovskites and the superior stability of layered perovskites and gradually get hotspots of the photovoltaic field. In addition, there remains a lack of comprehensive understanding and systematic summary of the function of 2D perovskite attributed to the complex nature of 2D/3D structures. Here, the latest progress of 2D/3D hybrid structures and focus on the functionality of 2D phases in mixed structures and the underlying mechanism from the perspective of their different distributions in the perovskite layer is summarized. Then, the insight and vital factors for overall improvements in the stability of 2D/3D structures are thoroughly discussed. Finally, it is expected that this review will contribute to the present challenges and future research prospects in the photovoltaic industry.     

Exciton Dynamics and Optically Pumped Lasing in 1-Naphthylmethylamine-Based Quasi-2D Perovskite Films

Films of the quasi-2D perovskite based on 1-naphthylmethylamine (NMA) are promising as the gain medium for optically pumped lasing and future electrically pumped lasing because of its low lasing threshold and small electroluminescence efficiency rolloff. However, reasons for the low threshold and small efficiency rolloff are still unclear. Therefore, exciton dynamics are investigated in NMA-based quasi-2D perovskite films. It is found that quenching of bright excitons by other excitons or charge carriers is unlikely in NMA-based quasi-2D perovskite films, which is one reason for the low lasing threshold and small efficiency rolloff. Moreover, thermally stimulated current measurements reveal that the defect levels inside the band gap of the NMA-based quasi-2D perovskite are shallow, with a depth of ≈0.3 eV, causing a decrease in nonradiative exciton recombination through the defects. Therefore, population inversion can be easily achieved, leading to the low lasing threshold as well. For fabrication of NMA-based quasi-2D perovskite laser devices with even lower lasing thresholds, a circular-shaped optical resonator, and small-molecule-based defect passivation are used. Optically pumped lasing can be obtained from these devices, with a threshold of ≈1 µJ cm⁻², which is one of the lowest values ever reported in any perovskite lasers.     

3D/2D Perovskite Single Crystals Heterojunction for Suppressed Ions Migration in Hard X-Ray Detection

Halide perovskites exhibit diverse properties depending on their compositions. However, integrating desired properties into one material is still challenging. Here, a facile solution-processed epitaxial growth method to grow 2D perovskite single crystal on top of 3D perovskite single crystal, which can passivate the surface defects for improved device performance is reported. Short formamidine (FA⁺) ions are replaced by long organic cations, which can fully align and cover the single crystal surface to prevent the ions migration or short FA⁺ ions volatilization. The thickness of epitaxial layer can be finely adjusted by controlling the growth time. The defect density of single crystals heterojunction is only 3.18 × 10⁹ cm⁻³, and the carrier mobility is 80.43 cm² V⁻¹ s⁻¹, which is greater than that of the control 3D perovskite single crystal. This study for the first time realized large area 3D/2D perovskite single crystals heterojunction, which suppressed ions migration and exhibited advanced performance in hard X-rays detection applications. This strategy also provides a way to grow large area 2D perovskite single crystal from solution processes.     

2D/2D Heterojunction of Ultrathin MXene/Bi2WO6 Nanosheets for Improved Photocatalytic CO2 Reduction

Exploring cheap and efficient cocatalysts for enhancing the performance of photocatalysts is a challenge in the energy conversion field. Herein, 2D ultrathin Ti₃C₂ nanosheets, a kind of MXenes, are prepared by etching Ti₃AlC₂ with subsequent ultrasonic exfoliation. A novel 2D/2D heterojunction of ultrathin Ti₃C₂/Bi₂WO₆ nanosheets is then successfully prepared by in situ growth of Bi₂WO₆ ultrathin nanosheets on the surface of these Ti₃C₂ ultrathin nanosheets. The resultant Ti₃C₂/Bi₂WO₆ hybrids exhibit a short charge transport distance and a large interface contact area, assuring excellent bulk‐to‐surface and interfacial charge transfer abilities. Meanwhile, the improved specific surface area and pore structure endow Ti₃C₂/Bi₂WO₆ hybrids with an enhanced CO₂ adsorption capability. As a result, the 2D/2D heterojunction of ultrathin Ti₃C₂/Bi₂WO₆ nanosheets shows significant improvement on the performance of photocatalytic CO₂ reduction under simulated solar irradiation. The total yield of CH₄ and CH₃OH obtained on the optimized Ti₃C₂/Bi₂WO₆ hybrid is 4.6 times that obtained on pristine Bi₂WO₆ ultrathin nanosheets. This work provides a new protocol for constructing 2D/2D photocatalytic systems and demonstrates Ti₃C₂ as a promising and cheap cocatalyst.     

High Performance BiOCl Nanosheets/TiO2 Nanotube Arrays Heterojunction UV Photodetector: The Influences of Self‐Induced Inner Electric Fields in the BiOCl Nanosheets

BiOCl nanosheets/TiO₂ nanotube arrays heterojunction UV photodetector (PD) with high performance is fabricated by a facile anodization process and an impregnation method. The heterojunction at the interface and the internal electric fields in the BiOCl nanosheets faciliate the separation of photogenerated charge carriers and regulate the transportation of the electrons. Compared with the large dark current (≈10^?5 A), low on/off ratio (8.5), and slow decay time (>60 s) of the TiO₂ PD, the optimized heterojunction PD (6‐BiOCl–TiO₂) yields dramatically decreased dark current (≈1 nA), ultrahigh on/off ratio (up to 2.2 × 10⁵), and fast decay speed (0.81 s) under 350 nm light illumination at ?5 V. Moreover, it exhibits an increased responsivity of 41.94 A W^?1, a remarkable detectivity (D*) of 1.41 × 10¹⁴ Jones, and a high linear dynamic range of 103.59 dB. The loading amount and growth orientations of the BiOCl nanosheets alter the roles of the self‐induced internal electric field in regulating the behaviors of the charge carriers, thus affecting the photoelectric properties of the heterojunction PDs. These results demonstrate that rational construction of novel heterojunctions hold great potentials for fabricating photodetectors with high performance.     

2D/3D Heterostructure for Semitransparent Perovskite Solar Cells with Engineered Bandgap Enables Efficiencies Exceeding 25% in Four‐Terminal Tandems with Silicon and CIGS

Wide‐bandgap perovskite solar cells (PSCs) with optimal bandgap (E_g) and high power conversion efficiency (PCE) are key to high‐performance perovskite‐based tandem photovoltaics. A 2D/3D perovskite heterostructure passivation is employed for double‐cation wide‐bandgap PSCs with engineered bandgap (1.65 eV ≤ E_g ≤ 1.85 eV), which results in improved stabilized PCEs and a strong enhancement in open‐circuit voltages of around 45 mV compared to reference devices for all investigated bandgaps. Making use of this strategy, semitransparent PSCs with engineered bandgap are developed, which show stabilized PCEs of up to 25.7% and 25.0% in four‐terminal perovskite/c‐Si and perovskite/CIGS tandem solar cells, respectively. Moreover, comparable tandem PCEs are observed for a broad range of perovskite bandgaps. For the first time, the robustness of the four‐terminal tandem configuration with respect to variations in the perovskite bandgap for two state‐of‐the‐art bottom solar cells is experimentally validated.     

In Situ Photosynthesis of an MAPbI3/CoP Hybrid Heterojunction for Efficient Photocatalytic Hydrogen Evolution

Halide perovskite like methylammonium lead iodide perovskite (MAPbI₃) with its prominent optoelectronic properties has triggered substantial concerns in photocatalytic H₂ evolution. In this work, to attain preferable photocatalytic performance, a MAPbI₃/cobalt phosphide (CoP) hybrid heterojunction is constructed by a facile in situ photosynthesis approach. Systematic investigations reveal that the CoP nanoparticle can work as co‐catalyst to not only extract photogenerated electrons effectively from MAPbI₃ to improve the photoinduced charge separation, but also facilitate the interfacial catalytic reaction. As a result, the as‐achieved MAPbI₃/CoP hybrid displays a superior H₂ evolution rate of 785.9 µmol h^?1 g^?1 in hydroiodic acid solution within 3 h, which is ≈8.0 times higher than that of pristine MAPbI₃. Furthermore, the H₂ evolution rate of MAPbI₃/CoP hybrid can reach 2087.5 µmol h^?1 g^?1 when the photocatalytic reaction time reaches 27 h. This study employs a facile in situ photosynthesis strategy to deposit the metal phosphide co‐catalyst on halide perovskite nanocrystals to conduct photocatalytic H₂ evolution reaction, which may stimulate the intensive investigation of perovskite/co‐catalyst hybrid systems for future photocatalytic applications.     

High‐Performance Ultraviolet Photodetector Based on a Few‐Layered 2D NiPS3 Nanosheet

2D materials, represented by transition metal dichalcogenides (TMDs), have attracted tremendous research interests in photoelectronic and electronic devices. However, for their relatively small bandgap (<2 eV), the application of traditional TMDs into solar‐blind ultraviolet (UV) photodetection is restricted. Here, for the first time, NiPS₃ nanosheets are grown via chemical vapor deposition method. The nanosheets thinning to 3.2 nm with the lateral size of dozens of micrometers are acquired. Based on the various nanosheets, a linearity is found between the Raman intensity of specific A_g modes and the thickness, providing a convenient method to determine their layer numbers. Furthermore, a UV photodetector is fabricated using few‐layered 2D NiPS₃ nanosheets. It shows an ultrafast rise time shorter than 5 ms with an ultralow dark current less than 10 fA. Notably, this UV photodetector demonstrates a high detectivity of 1.22 × 10¹² Jones, outperforming some traditional wide‐bandgap UV detectors. The wavelength‐dependent photoresponsivity measurement allows the direct observation of an admirable cut‐off wavelength at 360 nm, which indicates a superior spectral selectivity. The promising photodetector performance, accompanied with the controllable fabrication and transfer process of nanosheet, lays the foundation of applying 2D semiconductors for ultrafast UV light detection.     

The Electronic Properties of a 2D Ruddlesden-Popper Perovskite and its Energy Level Alignment with a 3D Perovskite Enable Interfacial Energy Transfer

The success of using 2D Ruddlesden-Popper metal halide perovskites (MHPs) in optoelectronic devices has ignited great interest as means for energy level tuning at the interface with 3D MHPs. Inter alia, the application of 2D phenylethylammonium lead quaternary iodide (PEA₂PbI₄)/3D MHPs interfaces has improved various optoelectronic devices, where a staggered type-II energy level alignment is often assumed. However, a type-II heterojunction seems to contradict the enhanced photoluminescence observed for 2D PEA₂PbI₄/3D MHP interfaces, which raises fundamental questions about the electronic properties of such junctions. In this study, using direct and inverse photoelectron spectroscopy, it is revealed that a straddling type-I energy level alignment is present at 2D PEA₂PbI₄/3D methylammonium lead triiodide (MAPbI₃) interfaces, thus explaining that the photoluminescence enhancement of the 3D perovskite is induced by energy transfer from the 2D perovskite. These results provide a reliable fundamental understanding of the electronic properties at the investigated 2D/3D MHP interfaces and suggest careful (re)consideration of the electronic properties of other 2D/3D MHP heterostructures.     

A Spacer Cation Assisted Nucleation and Growth Strategy Enables Efficient and High-Luminance Quasi-2D Perovskite LEDs

Quasi-2D Ruddlesden-Popper perovskites receive tremendous attention for application in light-emitting diodes (LEDs). However, the role of organic ammonium spacers on perovskite film has not been fully-understood. Herein, a spacer cation assisted perovskite nucleation and growth strategy, where guanidinium (GA⁺) spacer is introduced into the perovskite precursor and at the interface between the hole transport layer (HTL) and the perovskite, to achieve dense and uniform perovskite films with enhanced optical and electrical performance is developed. A thin GABr interface pre-formed on HTL provides more nucleation sites for perovskite crystal; while the added GA⁺ in perovskite reduces the crystallization rate due to strong hydrogen bonding interacts with intermediates, which promotes the growth of enhanced-quality quasi-2D perovskite films. The ionized ammonium group ( NH₃⁺) of GA⁺ also favors formation of polydisperse domain distribution, and amine or imine ( NH₂ or NH) group interact with perovskite defects through coordination bonding. The spacer cation assisted nucleation and growth strategy is advantageous for producing efficient and high-luminance perovskite LEDs, with a peak external quantum efficiency of over 20% and a luminance up to 100 000 cd m⁻². This work can inform and underpin future development of high-performance perovskite LEDs with concurrent high efficiency and brightness.     

In Situ Fabrication of Highly Luminescent Bifunctional Amino Acid Crosslinked 2D/3D NH3C4H9COO(CH3NH3PbBr3)n Perovskite Films

The perovskite quantum dots are usually synthesized by solution chemistry and then fabricated into film for device application with some extra process. Here it is reported for the first time to in situ formation of a crosslinked 2D/3D NH₃C₄H₉COO(CH₃NH₃) _n Pb_n Br_3n perovskite planar films with controllable quantum confine via bifunctional amino acid crosslinkage, which is comparable to the solution chemistry synthesized CH₃NH₃PbBr₃ quantum dots. These atomic layer controllable perovskite films are facilely fabricated and tuned by addition of bi‐functional 5‐aminovaleric acid (Ava) of NH₂C₄H₉COOH into regular (CH₃NH₃)PbBr₃ (MAPbBr₃) perovskite precursor solutions. Both the NH₃⁺ and the COO^? groups of the zwitterionic amino acid are proposed to crosslink the atomic layer MAPbBr₃ units via Pb? COO bond and ion bond between NH₃⁺ and [PbX₆] unit. The characterizations by atomic force microscopy, scanning electron microscopy, Raman, and photoluminescence spectroscopy confirm a successful fabrication of ultrasmooth and stable film with tunable optical properties. The bifunctional crosslinked 2D/3D Ava(MAPbBr₃)_n perovskite films with controllable quantum confine would serve as distinct and promising materials for optical and optoelectronic applications.     

Efficient Blue Perovskite Light‐Emitting Diodes Boosted by 2D/3D Energy Cascade Channels

Lead halide perovskite, as an emerging semiconductor, provides a fire‐new opportunity for high‐definition display and solid‐state lighting. Earthshaking improvements are implemented in green, red, and near‐infrared perovskite light‐emitting diodes (PeLEDs). However, blue PeLEDs are still far behind in performance, which restricts the development of PeLEDs in practical applications. Herein, a facile energy cascade channel strategy via one‐step self‐organized and controllable 2D/3D perovskite preparation by introducing guanidine hydrobromide (GABr) is developed that greatly improves the efficiency of blue PeLEDs. The 2D/3D perovskite structure boosts the energy cascade to induce energy transfer from the wide into the narrow bandgap domains and inhibit free charge diffusion, which increases the density of electrons and holes, and enhances the radiative recombination. Profiting from this energy cascade channels, the external quantum efficiency of blue PeLEDs, emitting at 492 nm, is considerably enhanced from 1.5% of initial blue device to 8.2%. In addition, device operating stability under ambient conditions is also improved by 2.6‐fold. The one‐step self‐organized 2D/3D hybrid perovskites induced by GABr pave a new and simple route toward high‐performance blue emission PeLEDs.