Synergistic passivation and stepped-dimensional perovskite analogs enable high-efficiency near-infrared light-emitting diodes

Efficient and stable blue perovskite light-emitting diodes enabled by the synergistic incorporation of dual additives

Perovskite materials have garnered significant attention in the field of light-emitting diodes (LEDs) due to their low cost, solution processing, straightforward fabrication, tunable emission wavelengths, narrow emission linewidths, and high photoluminescence quantum yield. However, blue perovskite light-emitting diodes (PeLEDs) currently face challenges of low efficiency and poor stability, which hinder their application in full-color display technology. It is understood that the quality of the perovskite film is considered a key factor affecting the performance of PeLEDs. To achieve high-quality perovskite films and high-performance PeLEDs, benzoic acid potassium (BAP) and guanidinium chloride (GACl) were employed as dual additives in the precursor solution of a quasi-two-dimensional perovskite (PEA2Csn-1PbnX3n+1). By utilizing the coordination of BA- from BAP with uncoordinated Pb2+ and the formation of hydrogen bonds between GA+ from GACl and halide ions, the perovskite surface defects are effectively passivated, along with the inhibition of the migration of halide ions. This approach reduces non-radiative recombination and enhances the spectral stability of perovskite films. By fine-tuning the concentrations of BAP and GACl, optimal PeLEDs are achieved at a BAP concentration of 3% and a GACl concentration of 10%, with the spectrum stabilized at 476 nm and a maximum external quantum efficiency (EQEmax) of 4.47%, which is 2.54 times that of the control device (EQEmax of 1.76%). The findings in this study provide a new approach for the fabrication of highly efficient and spectrally stable blue PeLEDs.

High-Brightness Perovskite Light-Emitting Diodes with Suppressed Efficiency Roll-off Using the Green Solvent γ-Valerolactone

The application of promising perovskite light-emitting diodes (PeLEDs) faces a significant challenge known as efficiency roll-off, which refers to the decline in external quantum efficiency (EQE) at high current densities. This issue arises mainly from high trap densities in perovskite films and imbalanced carrier injection, which limit improvements in brightness and stability of PeLEDs. Here, we develop a green solvent strategy using γ-valerolactone (GVL) to suppress efficiency roll-off in PeLEDs. This strategy effectively slows down the crystallization kinetics, yielding cubic-phase formamidinium lead triiodide (α-FAPbI3) films with reduced trap states, enhanced charge carrier injection, and suppressed Auger recombination. As a result, we achieve a record radiance of 1411 W sr-1 m-2 for GVL-based PeLEDs. These PeLEDs exhibit a substantially reduced efficiency roll-off, maintaining an EQE above 20% even at a high current density of 900 mA cm-2. Our findings highlight the potential of the green solvent approach for developing high-brightness, high-efficiency PeLEDs for practical applications.

Perovskite heteroepitaxy for high-efficiency and stable pure-red LEDs

Ultrasmall CsPbI3 perovskite quantum dots (QDs) are the most promising candidates for realizing efficient and stable pure-red perovskite light-emitting diodes (PeLEDs)1-5. However, it is challenging for ultrasmall CsPbI3 QDs to retain their solution-phase properties when they assemble into conductive films, greatly hindering their device application3,6. Here we report an approach for in situ deposit stabilized ultrasmall CsPbI3 QD conductive solids, by constructing CsPbI3 QD/quasi-two-dimensional (quasi-2D) perovskite heteroepitaxy. The well-aligned periodic array of edge-oriented ligands at heterointerface triggers a substantial octahedral tilting in a critical layer thickness of CsPbI3 QDs, which heightens the Gibbs free energy difference between the tilted-CsPbI3 and δ-CsPbI3 leading to thermodynamic stabilization of CsPbI3 QDs. The approach allows us to fabricate stabilized CsPbI3 QD conductive films with tunable emission covering the entire red spectral region from 600 nm to 710 nm. Here we report the pure-red PeLEDs with narrow electroluminescence peak centred at 630 nm, matching the Rec. 2100 standard for ultrahigh-definition display. The champion device exhibits a certified external quantum efficiency of 24.6% and a half-lifetime of 6,330 min, ranking as one of the most efficient and stable pure-red PeLED reported to date. The approach is also compatible with large-area manufacturing, enabling 1 cm2 PeLED to exhibit the best external quantum efficiency of 20.5% at 630 nm.

Enhanced Hole-Injecting Interface for High-Performance Deep-Blue Perovskite Light-Emitting Diodes Using Dipole-Controlled Self-Assembled Monolayers

The Blue electroluminescence (EL) with high brightness and spectral stability is imperative for full-color perovskite display technologies meeting the Rec. 2020 standard. However, deep-blue perovskite light-emitting diodes (PeLEDs) lag behind their green- or red-emitting counterparts in brightness, quantum efficiency, and operational stability. Additionally, the Cl-/Br- mixed-halide perovskites with wide bandgap typically designed for deep-blue emitters are prone to degradation quickly under high operating bias due to low energy for halide migrations and vacancies formation, posing a significant challenge to spectral/operative stabilities. To address these issues, high-performance deep-blue PeLEDs are demonstrated by tuning the interface properties with Br-2ETP, a self-assembled monolayer (SAM) molecule engineered for a high dipole moment. The Br-2EPT-based hole-injecting interface facilitates favorable energy level alignment between indium tin oxide and the deep-lying valence band of the perovskite layer, suppressing the hole-injecting barrier and non-radiative charge recombination. Excellent perovskite film morphologies are observed at the top and buried surfaces by Br-2EPT, improving the balance of carrier injection for light emission efficiency. Consequently, the devices exhibit deep-blue electroluminescence at 457 nm, with an external quantum efficiency of 6.56% and spectral/operative stabilities.

Grain engineering for efficient near-infrared perovskite light-emitting diodes

Metal halide perovskites show promise for next-generation light-emitting diodes, particularly in the near-infrared range, where they outperform organic and quantum-dot counterparts. However, they still fall short of costly III-V semiconductor devices, which achieve external quantum efficiencies above 30% with high brightness. Among several factors, controlling grain growth and nanoscale morphology is crucial for further enhancing device performance. This study presents a grain engineering methodology that combines solvent engineering and heterostructure construction to improve light outcoupling efficiency and defect passivation. Solvent engineering enables precise control over grain size and distribution, increasing light outcoupling to ~40%. Constructing 2D/3D heterostructures with a conjugated cation reduces defect densities and accelerates radiative recombination. The resulting near-infrared perovskite light-emitting diodes achieve a peak external quantum efficiency of 31.4% and demonstrate a maximum brightness of 929 W sr-1 m-2. These findings indicate that perovskite light-emitting diodes have potential as cost-effective, high-performance near-infrared light sources for practical applications.

Enhanced light extraction by optimizing near-infrared perovskite-based light emitting diode (PeLED)

One of the outstanding optoelectronic devices is perovskite-based light emitting diodes (PeLEDs) that have diverse applications according to the wavelength of produced light. However, these devices have shown more than 20% External Quantum Efficiency (EQE), in comparison with their counterparts (OLEDs), light extraction is limited in these devices. In this paper, by optimizing the thickness of layers and manipulating absorption in the active layer (AL), the light extraction efficiency (LEE) increased by nearly 20%. It reached 42.89% in the near-infrared (NIR) region of the wavelength, by considering the CH(NH2)2PbI3 perovskite, in the emissive layer (EML).

Homogenizing Energy Landscape for Efficient and Spectrally Stable Blue Perovskite Light-Emitting Diodes

Blue perovskite light-emitting diodes (PeLEDs) have attracted enormous attention; however, their unsatisfactory device efficiency and spectral stability still remain great challenges. Unfavorable low-dimensional phase distribution and defects with deeper energy levels usually cause energy disorder, substantially limiting the device's performance. Here, an additive-interface optimization strategy is reported to tackle these issues, thus realizing efficient and spectrally stable blue PeLEDs. A new type of additive-formamidinium tetrafluorosuccinate (FATFSA) is introduced into the quasi-2D mixed halide perovskite accompanied by interface engineering, which effectively impedes the formation of undesired low-dimensional phases with various bandgaps throughout the entire film, thereby boosting energy transfer process for accelerating radiative recombination; this strategy also diminishes the halide vacancies especially chloride-related defects with deep energy level, thus reducing nonradiative energy loss for efficient radiative recombination. Benefitting from homogenized energy landscape throughout the entire perovskite emitting layer, PeLEDs with spectrally-stable blue emission (478 nm) and champion external quantum efficiency (EQE) of 21.9% are realized, which represents a record value among this type of PeLEDs in the pure blue region.

Efficient and Stable Red Perovskite Light-Emitting Diodes via Thermodynamic Crystallization Control

Efficient and stable red perovskite light-emitting diodes (PeLEDs) demonstrate promising potential in high-definition displays and biomedical applications. Although significant progress has been made in device performance, meeting commercial demands remains a challenge in the aspects of long-term stability and high external quantum efficiency (EQE). Here, an in situ crystallization regulation strategy is developed for optimizing red perovskite films through ingenious vapor design. Mixed vapor containing dimethyl sulfoxide and carbon disulfide (CS2) is incorporated to conventional annealing, which contributes to thermodynamics dominated perovskite crystallization for well-aligned cascade phase arrangement. Additionally, the perovskite surface defect density is minimized by the CS2 molecule adsorption. Consequently, the target perovskite films exhibit smooth exciton energy transfer, reduced defect density, and blocked ion migration pathways. Leveraging these advantages, spectrally stable red PeLEDs are obtained featuring emission at 668, 656, and 648 nm, which yield record peak EQEs of 30.08%, 32.14%, and 29.04%, along with prolonged half-lifetimes of 47.7, 60.0, and 43.7 h at the initial luminances of 140, 250, and 270 cd m-2, respectively. This work provides a universal strategy for optimizing perovskite crystallization and represents a significant stride toward the commercialization of red PeLEDs.

Modulation of Charge Transport Layer for Perovskite Light-Emitting Diodes

Perovskite light-emitting diodes (Pero-LEDs) have garnered significant attention due to their exceptional emission characteristics, including narrow full width at half maximum, high color purity, and tunable emission colors. Recent efficiency and operational stability advancements have positioned Pero-LEDs as a promising next-generation display technology. Extensive research and review articles on the compositional engineering and defect passivation of perovskite layers have substantially contributed to the development of multi-color and high-efficiency Pero-LEDs. However, the crucial aspect of charge transport layer (CTL) modulation in Pero-LEDs remains relatively underexplored. CTL modulation not only impacts the charge carrier transport efficiency and injection balance but also plays a critical role in passivating the perovskite surface, blocking ion migration, enhancing perovskite crystallinity, and improving light extraction efficiency. Therefore, optimizing CTLs is pivotal for further enhancing Pero-LED performance. Herein, this review discusses the roles of CTLs in Pero-LEDs and categorizes both reported and potential CTL materials. Then, various CTL optimization strategies are presented, alongside an analysis of the selection criteria for CTLs in high-performance Pero-LEDs. Finally, a summary and outlook on the potential of CTL modulation to further advance Pero-LED performances are provided.

Thin Film Stoichiometry and Defects Management for Low Threshold and Air Stable Near-Infrared Perovskite Laser

While significant efforts have been devoted to optimize the thin-film stoichiometry and processing of perovskites for applications in photovoltaic and light-emitting diodes, there is a noticeable lack of emphasis on tailoring them for lasing applications. In this study, it is revealed that thin films engineered for efficient light-emitting diodes, with passivation of deep and shallow trap states and a tailored energetic landscape directing carriers toward low-energy emitting states, may not be optimal for light amplification systems. Instead, amplified spontaneous emission (ASE) is found to be sustained by shallow defects, driven by the positive correlation between the ASE threshold and the ratio of carrier injection rate in the emissive state to the recombination rate of excited carriers. This insight has informed the development of an optimized perovskite thin film and laser device exhibiting a low threshold (≈ 60 µJ cm-2) and stable ASE emission exceeding 21 hours in ambient conditions.

Amorphous (lysine)2PbI2 layer enhanced perovskite photovoltaics

Passivation materials play a crucial role in a wide range of high-efficiency, high-stability photovoltaic applications based on crystalline silicon and state-of-the-art perovskite materials. Currently, for perovskite photovoltaic, the mainstream passivation strategies routinely rely on crystalline materials. Herein, we have invented a new amorphous (lysine)2PbI2 layer-enhanced halide perovskite. By utilizing a solid phase reaction between PbI2 and lysine molecule, an amorphous (lysine)2PbI2 layer is formed at surface/grain boundaries in the perovskite films. The amorphous (lysine)2PbI2 with fewer dangling bonds can effectively neutralize surface/interface defects, achieving an impressive efficiency of 26.27% (certified 25.94%). Moreover, this amorphous layer not only reduces crystal lattice stress but also functions as a barrier against the decomposition of organic components, leading to suppressed de-structuring of perovskite and highly stable perovskite solar cells.

Elevating Charge Transport Layer for Stable Perovskite Light-Emitting Diodes

Ion migration is a major factor affecting the long term stability of perovskite light-emitting diodes (LEDs), which limits their commercialization potential. The accumulation of excess halide ions at the grain boundaries of perovskite films is a primary cause of ion migration in these devices. Here, it is demonstrated that the channels of ion migrations can be effectively impeded by elevating the hole transport layer between the perovskite grain boundaries, resulting in highly stable perovskite LEDs. The unique structure is achieved by reducing the wettability of the perovskites, which prevents infiltration of the upper hole-transporting layer into the spaces of perovskite grain boundaries. Consequently, nanosized gaps are formed between the excess halide ions and the hole transport layer, effectively suppressing ion migration. With this structure, perovskite LEDs with operational half-lifetimes of 256 and 1774 h under current densities of 100 and 20 mA cm-2 respectively are achieved. These lifetimes surpass those of organic LEDs at high brightness. It is further found that this approach can be extended to various perovskite LEDs, showing great promise for promoting perovskite LEDs toward commercial applications.

Buried interface modification and light outcoupling strategy for efficient blue perovskite light-emitting diodes

Perovskite light-emitting diodes (PeLEDs) exhibit remarkable potential in the field of displays and solid-state lighting. However, blue PeLEDs, a key element for practical applications, still lag behind their green and red counterparts, due to a combination of strong nonradiative recombination losses and unoptimized device structures. In this report, we propose a buried interface modification strategy to address these challenges by focusing on the bottom-hole transport layer (HTL) of the PeLEDs. On the one hand, a multifunctional molecule, aminoacetic acid hydrochloride (AACl), is introduced to modify the HTL/perovskite interface to regulate the perovskite crystallization. Experimental investigations and theoretical calculations demonstrate that AACl can effectively reduce the nonradiative recombination losses in bulk perovskites by suppressing the growth of low-n perovskite phases and also the losses at the bottom interface by passivating interfacial defects. On the other hand, a self-assembly nanomesh structure is ingeniously developed within the HTLs. This nanomesh structure is meticulously crafted through the blending of poly-(9,9-dioctyl-fluorene-co-N-(4-butyl phenyl) diphenylamine) and poly (n-vinyl carbazole), significantly enhancing the light outcoupling efficiency in PeLEDs. As a result, our blue PeLEDs achieve remarkable external quantum efficiencies, 20.4% at 487 nm and 12.5% at 470 nm, which are among the highest reported values. Our results offer valuable insights and effective methods for achieving high-performance blue PeLEDs.

Highly efficient blue light-emitting diodes based on mixed-halide perovskites with reduced chlorine defects

Perovskite light-emitting diodes (PeLEDs) provide excellent opportunities for low-cost, color-saturated, and large-area displays. However, the performance of blue PeLEDs lags far behind that of their green and red counterparts. Here, we show that the external quantum efficiencies (EQEs) of blue PeLEDs scale linearly with the photoluminescence quantum yields (PL QYs) of CsPb(BrxCl1-x)3 nanocrystals emitting at 460 to 480 nm. The recombination efficiency of carriers is highly sensitive to the chlorine content and the related deep-level defects in nanocrystals, causing notable EQE drops even with minor increases in chlorine defects. Minor adjustments of chlorine content through rubidium compensation on the A-site effectively suppress the formation of nonradiative defects, improving PL QYs while retaining desirable bandgaps for blue-emitting nanocrystals. Our PeLEDs with record-high efficiencies span the blue spectrum, achieving peak EQEs of 12.0% (460 nm), 16.7% (465 nm), 21.3% (470 nm), 24.3% (475 nm), and 26.4% (480 nm). This work exemplifies chlorine-defect control as a key design principle for high-efficiency blue PeLEDs.

Efficient and stable hybrid perovskite-organic light-emitting diodes with external quantum efficiency exceeding 40 per cent

Light-emitting diodes (LEDs) based on perovskite semiconductor materials with tunable emission wavelength in visible light range as well as narrow linewidth are potential competitors among current light-emitting display technologies, but still suffer from severe instability driven by electric field. Here, we develop a stable, efficient and high-color purity hybrid LED with a tandem structure by combining the perovskite LED and the commercial organic LED technologies to accelerate the practical application of perovskites. Perovskite LED and organic LED with close photoluminescence peak are selected to maximize photon emission without photon reabsorption and to achieve the narrowed emission spectra. By designing an efficient interconnecting layer with p-type interface doping that provides good opto-electric coupling and reduces Joule heating, the resulting green emitting hybrid LED shows a narrow linewidth of around 30 nm, a peak luminance of over 176,000 cd m-2, a maximum external quantum efficiency of over 40%, and an operational half-lifetime of over 42,000 h.

Vertically Concentrated Quantum Wells Enabling Highly Efficient Deep-Blue Perovskite Light-Emitting Diodes

Deep-blue perovskite light-emitting diodes (PeLEDs) based on quasi-two-dimensional (quasi-2D) systems exist heightened sensitivity to the domain distribution. The top-down crystallization mode will lead to a vertical gradient distribution of quantum well (QW) structure, which is unfavorable for deep-blue emission. Herein, a thermal gradient annealing treatment is proposed to address the polydispersity issue of vertical QWs in quasi-2D perovskites. The formation of large-n domains at the upper interface of the perovskite film can be effectively inhibited by introducing a low-temperature source in the annealing process. Combined with the utilization of NaBr to inhibit the undesirable n=1 domain, a vertically concentrated QW structure is ultimately attained. As a result, the fabricated device delivers a narrow and stable deep-blue emission at 458 nm with an impressive external quantum efficiency (EQE) of 5.82 %. Green and sky-blue PeLEDs with remarkable EQE of 21.83 % and 17.51 % are also successfully achieved, respectively, by using the same strategy. The findings provide a universal strategy across the entire quasi-2D perovskites, paving the way for future practical application of PeLEDs.

Dielectric Regulation for Efficient Top-Emission Perovskite Light-Emitting Diodes with Suppressed Efficiency Roll-off

Perovskite light-emitting diodes (PeLEDs) have shown incalculable application potential in the fields of next-generation displays and light communication owing to the rapidly increased external quantum efficiencies (EQEs). However, most PeLEDs obtain a maximum EQE at small current density (J) region and suffer from severe efficiency roll-off in different extents. Herein, it is demonstrated that the dopant with large dipole moment like KBF4 facilitates the effective dielectric regulation of perovskite emissive layer. The increased dielectric constant lowers the exciton binding energy and suppresses the Auger recombination of the 2D/3D segregated perovskite structure, which improves the photoluminescence quantum yield remarkably at an excitation intensity up to 103 mW cm-2. Accordingly, the top-emission PeLED that delivers a high maximum EQE above 20% is fabricated and can retain EQE > 10% at an extremely high J of 708 mA cm-2. These results represent one of the most efficient top-emission PeLEDs with ultra-low efficiency roll-off, which provide a viable methodology for tuning the dielectric response of perovskite films for improved high radiance performance of perovskite electroluminescence devices.

Controlling Interfacial Amidation Reaction Rate to Regulate Crystal Growth toward High-Performance FAPbBr3-Based Inverted Light-Emitting Diodes

Controlling interfacial reactions is critical for zinc oxide (ZnO)-based inverted perovskite light-emitting diodes (PeLEDs), boosting the external quantum efficiency (EQE) of the near-infrared device to above 20%. However, violent interfacial reactions between the bromine-based perovskites and ZnO-based films severely limit the performance of inverted green PeLEDs, whose efficiency and stability lag far behind those of their near-infrared counterparts. Here, a controllable interfacial amidation between the bromine-based perovskites and magnesium-doped ZnO (ZnMgO) film utilizing caprylyl sulfobetaine (SFB) is realized. The SFB molecules strongly interact with formamidinium bromide, decelerating the amidation reaction between formamidinium and carboxylate groups on the ZnMgO film, thus regulating the crystallization of FAPbBr3. Combined with the passivation of benzylamine, a FAPbBr3 bulk film directly deposited on a ZnMgO substrate with single-crystal characteristics is obtained, exhibiting a high photoluminescence quantum yield of above 80%. The resultant PeLEDs demonstrate a peak EQE of exceeding 20% at a high luminance of 120,000 cd m-2 and a half lifetime of 26 min at 11,000 cd m-2, representing the state-of-the-art inverted green electroluminescence. This work resolves the crucial issues of violent interfacial reactions and provides a strategy toward inverted green PeLEDs with outstanding performance.

Unveiling the Dual Role of Humidity: The Interplay with Defects Manipulating the Charge Carrier Lifetime in Metal Halide Perovskites

Humidity has exhibited experimentally either beneficial or detrimental effects on the charge carrier lifetime of CH3NH3PbI3 perovskites, leaving the mechanism unresolved. By using ab initio nonadiabatic molecular dynamics simulations, we unveil the dual role of humidity stemming from the complex interplay between water and defects. Beneficially, water passivates iodine vacancies (VI) or grain boundaries (GBs), mitigating electron trapping by reducing nonadiabatic coupling and delaying charge recombination. However, when VI and GBs coexist, water molecules make the two unsaturated lead atoms approach closer and exacerbate electron trapping by deepening the Pb-dimer electron trap that was created by the VI defect, shortening the carrier lifetime to half of pristine CH3NH3PbI3. The study uncovers the origin of the positive and negative effects of humidity on the charge carrier lifetime of perovskites and offers strategies for improving perovskite devices, particularly by avoiding simultaneous point defects and GBs.

Flexible and Stretchable Light-Emitting Diodes and Photodetectors for Human-Centric Optoelectronics

Optoelectronic devices with unconventional form factors, such as flexible and stretchable light-emitting or photoresponsive devices, are core elements for the next-generation human-centric optoelectronics. For instance, these deformable devices can be utilized as closely fitted wearable sensors to acquire precise biosignals that are subsequently uploaded to the cloud for immediate examination and diagnosis, and also can be used for vision systems for human-interactive robotics. Their inception was propelled by breakthroughs in novel optoelectronic material technologies and device blueprinting methodologies, endowing flexibility and mechanical resilience to conventional rigid optoelectronic devices. This paper reviews the advancements in such soft optoelectronic device technologies, honing in on various materials, manufacturing techniques, and device design strategies. We will first highlight the general approaches for flexible and stretchable device fabrication, including the appropriate material selection for the substrate, electrodes, and insulation layers. We will then focus on the materials for flexible and stretchable light-emitting diodes, their device integration strategies, and representative application examples. Next, we will move on to the materials for flexible and stretchable photodetectors, highlighting the state-of-the-art materials and device fabrication methods, followed by their representative application examples. At the end, a brief summary will be given, and the potential challenges for further development of functional devices will be discussed as a conclusion.

A Multifunctional Additive Strategy Enables Efficient Pure-Blue Perovskite Light-Emitting Diodes

Lead halide perovskites have shown exceptional performance in light-emitting devices (PeLEDs), particularly in producing significant electroluminescence in sky-blue to near-infrared wavelengths. However, PeLEDs emitting pure-blue light at 465-475 nm are still not satisfactory. Herein, efficient and stable pure-blue PeLEDs are reported by controlling phase distribution, passivation of defects, as well as surface modifications using multifunctional phenylethylammonium trifluoroacetate (PEATFA) in reduced-dimensional p-F-PEA2 Csn-1 Pbn (Br0.55 Cl0.45 )3n+1 polycrystalline perovskite films. Compared with 4-fluorophenylethylammonium (p-F-PEA+ ) in the pristine films, phenylethylammonium (PEA+ ) has lower adsorption energy while interacting with perovskites, resulting in large-n low-dimensional perovskites, which can greatly facilitate charge transport within the low-dimensional perovskite films. The interaction between the CO group in trifluoroacetate (TFA- ) and perovskites significantly reduces defects in the perovskite films. Additionally, the electron-giving CF3 group in TFA- uplifts surface potential in the films, resulting in smooth electronic injection in devices. The multifunctional additive strategy leads to elevated radiative recombination and efficient carrier transport in the films and devices. As a result, the devices exhibit a maximum external quantum efficiency (EQE) of 11.87% at 468 nm with stable spectral output, the highest reported to date for pure-blue PeLEDs. Thus, this study extends the way for high-efficiency pure-blue LED with perovskite polycrystal films.

High Efficiency Near-Infrared Perovskite Light Emitting Diodes With Reduced Rolling-Off by Surface Post-Treatment

The rolling-off phenomenon of device efficiency at high current density caused by quenching of luminescence in perovskite light-emitting diodes (PeLED) is challenging to be solved. Here, 2-amino-5-iodopyrazine (AIPZ) is dissolved in a mixed solvent of chlorobenzene (CB)/isopropanol (IPA) (7:3 volume ratio) for surface post-treatment of FAPbI₃ perovskite film. The interaction of AIPZ and perovskite surface not only balances the charge injection but also passivates defects to enhance radiative recombination in PeLED. Therefore, the PeLED champion yields peak external quantum efficiency reaching 23.2% at the current density of 45 mA cm^-2 with a radiance brightness of 290 W sr^-1 m^-2 . More importantly, the rolling-off of device efficiency is significantly reduced. The lowest rolling-off devices can maintain 80% of peak EQE (22.1%) at a high current density of 460 mA cm^-2 , whereas the control device only retains 25% of the peak EQE value. This work provides an effective strategy to improve performance and reduce the EQE rolling-off of PeLED for practical application.