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Device structure and efficiency roll-off of perovskite MQW LEDs. a Schematic representation of the flat-band energy level diagram and structures of the 30-nm thick perovskite MQW film which is an assembly of different layered lead halide perovskites with various n numbers. The n number determines the bandgap of each quantum well. The MQW structure enhances the probability of radiative recombination. b Dependence of current density (blue triangles), normalized PLQE (black square), and EQE (red circle) on the driving voltage. The PLQE and EQE were measured simultaneously on a working LED device. The excellent correlation between the PLQE and EQE at high current intensities indicates that luminescence quenching is responsible for the EQE roll-off
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Efficiency roll-off is a major issue for most types of light-emitting diodes (LEDs), and its origins remain controversial. Here we present investigations of the efficiency roll-off in perovskite LEDs based on two-dimensional layered perovskites. By simultaneously measuring electroluminescence and photoluminescence on a working device, supported by...
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... By optimizing intrinsic material properties and designing rational device structures, the efficiencies of these devices have been significantly improved so far. 16,17 Despite these means, nontrivial physical processes of light-matter interactions, such as the photon recycling effect, can further promote device performances. [18][19][20][21] The photon recycling effect is a dynamical process where photons emitted by luminescent materials are reabsorbed during photon propagation paths, which will keep exciting the luminescent materials and spatiotemporally recycling photons. ...
Nanometer scale light penetration depths of halide perovskite (HP) set an intrinsic limit on the performance improvement of optoelectronic devices. Here, we show that two-photon excitation can overcome this limit by markedly increasing the light penetration depth and significantly enhance photon recycling. Through a comparison study between one-photon and two-photon excitations by femtosecond laser pulses in a CsPbBr3 nanosheet, our results demonstrate that two-photon excitation can increase photocarrier transport distance by about 900 nm, which is even comparable to the photocarrier diffusion length. Our work provides substantial insights into the photon recycling of HP induced by nonlinear optical excitations, which can benefit the performance optimization of advanced optoelectronic devices.
... Furthermore, the current density required for lasing applications, which are also electrically pumped, is typically greater than 100 A cm −2 . 28 Although high EQE is generally achieved at low current densities, studying the device behaviors at high current injection conditions (high luminance region) is more meaningful as it provides deeper understanding of EQE roll-off, 29,30 Auger recombination, 31,32 Joule heating, and so on. 18,33 Interfaces between Perovskite and Injection Layers. ...
Perovskite light-emitting diodes (LEDs) have emerged as one of the most propitious candidates for next-generation lighting and displays, with the highest external quantum efficiency (EQE) of perovskite LEDs already surpassing the 20% milestone. However, the further development of perovskite LEDs primarily relies on addressing operational instability issues. This Perspective examines some of the key factors that impact the lifetime of perovskite LED devices and some representative reports on recent advancements aimed at improving the lifetime. Our analysis underscores the significance of "nano" strategies in achieving long-term stable perovskite LEDs. Significant efforts must be directed toward proper device encapsulation, perovskite material passivation, interfacial treatment to address environment-induced material instability, bias-induced phase separation, and ion migration issues.
... Studies have shown that additives can effectively passivate surface defects of halide perovskites and reduce non-radiative recombination, thereby improving efficiency. In Figure 23, Zou found that by adjusting the proportion of large and small organic cations in the precursor solution, it was easy to increase the width of the quantum well in the halide perovskite, reduce the non-radiative Auger recombination, and reduce the fluorescence quenching to improve the efficiency [223]. Wu et al. added small basic ions such as Na + to replace the long organic molecules in the inorganic-organic perovskite to form a microcrystalline orientation [221]. ...
... Studies have shown that additives can effectively passivate surface defects of halide perovskites and reduce non-radiative recombination, thereby improving efficiency. In Figure 23, Zou found that by adjusting the proportion of large and small organic cations in the precursor solution, it was easy to increase the width of the quantum well in the halide perovskite, reduce the non-radiative Auger recombination, and reduce the fluorescence quenching to improve the efficiency [223]. ...
... Studies have shown that additives can effectively passivate surface defects of halide perovskites and reduce non-radiative recombination, thereby improving efficiency. In Figure 23, Zou found that by adjusting the proportion of large and small organic cations in the precursor solution, it was easy to increase the width of the quantum well in the halide perovskite, reduce the non-radiative Auger recombination, and reduce the fluorescence quenching to improve the efficiency [223]. In Figure 23b, the PLQE and EQE were measured simultaneously on a working LED device. ...
Halide perovskite materials have attracted worldwide attention in the photovoltaic area due to the rapid improvement in efficiency, from less than 4% in 2009 to 26.1% in 2023 with only a nanometer lever photo-active layer. Meanwhile, this nova star found applications in many other areas, such as light emitting, sensor, etc. This review started with the fundamentals of physics and chemistry behind the excellent performance of halide perovskite materials for photovoltaic/light emitting and the methods for preparing them. Then, it described the basic principles for solar cells and light emitting devices. It summarized the strategies including nanotechnology to improve the performance and the application of halide perovskite materials in these two areas: from structure–property relation to how each component in the devices affects the overall performance. Moreover, this review listed the challenges for the future applications of halide perovskite materials.
... For most LEDs, their efficiencies reduce at high current densities. This effect is called efficiency roll-off, which can be caused by a reduction in luminescence efficiency due to non-radiative processes and/or an excessive population of charge carriers passing through the device without forming electron-hole pairs [1,65,66]. The efficiency roll-off can be alleviated using doped charge-transport layers, materials with high charge-carrier mobility, and electrodes with low sheet resistance [67]. ...
The development of numerical models is essential for optimizing perovskite light-emitting diodes (PeLEDs) and explaining their physical mechanism for further efficiency improvement. This study reports, for the first time, on a detailed device modelling of an all-inorganic perovskite LED consisting of CsPbX3 (X=Br and I) as light emitting layer (LEL) with different hole transporting layers (HTLs), employing COMSOL Multiphysics simulation package. Therefore, a 3D simulation model is served to investigate the appropriate HTLs that meet the design requirements of a PeLED in terms of band off-set engineering. For this purpose, a series of all-inorganic halide perovskites with different HTLs are simulated under the same theoretical settings, and the performances of LEDs are compared with each other. This is done through studying their electronic properties using current density-voltage (J-V) characteristic curves and internal quantum efficiency (IQE) measurements. The results obtained from the J-V characteristics curve reveal that all the CsPbBr3-based samples with different HTLs exhibit the same turn-on voltage (Von) of approximately 4.2 V, while this value increases to 5.8 V for the CsPbI3-based samples. Compared with the PeLEDs based on CsPbI3, the PeLEDs based on CsPbBr3 indicate lower Von due to the formation of shorter charge carrier injection barriers at their interfaces. Furthermore, among the various simulated structures, the highest IQE is obtained for perovskite CsPbI3-based LED with MoO3 HTL (5.21%). The effect of different parameters on the performance of the proposed configurations are also investigated, and it turns out that the thickness of LELs and lifetime of charge carriers have a decisive role to play in the efficiency of PeLEDs. This theoretical study not only successfully explains the working principle of PeLEDs but also clearly shows researchers how to produce high-performance LEDs in the laboratory by knowing the physical properties of materials and accurately adjusting energy band alignments.
... The EQE roll-off is a general problem for all types of LED devices, especially in PeLEDs. It refers to the rapid decrease of EQE when LEDs are operated at a high current density, the major factors of EQE roll-off are unbalanced charge injection, Joule heating and Auger recombination [164][165][166][167]. The unbalanced charge injection can be ascribed to the inferior interface quality and inappropriate band alignment, and the unbalanced charge injection causes the carrier accumulation, leading to the aggravation of Auger recombination and Joule heating [68,154]. ...
Metal halide perovskites have shown excellent optoelectronic properties, including high photoluminescence quantum yield, tunable emission wavelength, narrow full-width at half-maximum and low-cost solution-processed fabrication, which make it exhibit great potential as the emission layer materials of light emitting diodes. With the joint efforts of researchers from different disciplines, there has been a significant progress in the improvement of external quantum efficiency (EQE) and stability of perovskite light emitting diodes (PeLEDs) in recent few years, especially in green PeLEDs with EQE over 30%. In this review, we firstly introduce the basic device structure of PeLEDs, as well as the factors influencing EQE and stability of PeLEDs. Secondly, the development of lead-based and lead-free PeLEDs are summarized systematically. Thirdly, challenges of PeLEDs are discussed in detail, including low EQE of blue PeLEDs, poor device stability and EQE roll-off. Finally, some suggestions and perspectives of the future research directions for PeLEDs are proposed.
... High-performance blue [103,109]-and white-emitting [110,111] devices are yet to be demonstrated, which are essential for display and solid-state lighting applications. Moreover, issues concerning efficiency roll-off [112] and lead toxicity in high-performance PeLEDs require further attention from researchers in the field. ...
... Low-dimensional perovskite has the potential to gain high PLQY due to its large exciton binding energy. The emission wavelength of quasi-2D perovskite mainly depend on the perovskite phase with the lowest bandgap, due to fast charge or energy transfer [112]. Therefore, it is necessary to control the phase distribution of perovskite. ...
... In general, low-dimensional perovskites or 3D perovskites with smaller crystal sizes suffer from severer Auger recombination due to the confinement of carries within the limited physical space, resulting in a high local carrier density [177,178]. Therefore, a straightforward way to suppress the Auger recombination is to enlarge the physical volume where recombination happens [112]. In addition, according to Fermi's golden rule, the possibility of inter-/ intra-band transitions between states positively correlate with their wave function overlapping. ...
Nowadays, the soar of photovoltaic performance of perovskite solar cells has set off a fever in the study of metal halide perovskite materials. The excellent optoelectronic properties and defect tolerance feature allow metal halide perovskite to be employed in a wide variety of applications. This article provides a holistic review over the current progress and future prospects of metal halide perovskite materials in representative promising applications, including traditional optoelectronic devices (solar cells, light-emitting diodes, photodetectors, lasers), and cutting-edge technologies in terms of neuromorphic devices (artificial synapses and memristors) and pressure-induced emission. This review highlights the fundamentals, the current progress and the remaining challenges for each application, aiming to provide a comprehensive overview of the development status and a navigation of future research for metal halide perovskite materials and devices.
... To reduce the unwanted nonradiative recombination rates, several methods have been proposed to lower the nonlinear process in 2D halide perovskites, including compositional engineering to increase the recombination centers in 2D systems, structural engineering, and tailoring the dielectric confinement by reducing the e-h overlap. 269,307 These methods aim to manipulate the dielectric screening by the organic layers, which brings down the exciton binding energy. ...
Three-dimensional (3D) organic-inorganic lead halide perovskites have emerged in the past few years as a promising material for low-cost, high-efficiency optoelectronic devices. Spurred by this recent interest, several subclasses of halide perovskites such as two-dimensional (2D) halide perovskites have begun to play a significant role in advancing the fundamental understanding of the structural, chemical, and physical properties of halide perovskites, which are technologically relevant. While the chemistry of these 2D materials is similar to that of the 3D halide perovskites, their layered structure with a hybrid organic-inorganic interface induces new emergent properties that can significantly or sometimes subtly be important. Synergistic properties can be realized in systems that combine different materials exhibiting different dimensionalities by exploiting their intrinsic compatibility. In many cases, the weaknesses of each material can be alleviated in heteroarchitectures. For example, 3D-2D halide perovskites can demonstrate novel behavior that neither material would be capable of separately. This review describes how the structural differences between 3D halide perovskites and 2D halide perovskites give rise to their disparate materials properties, discusses strategies for realizing mixed-dimensional systems of various architectures through solution-processing techniques, and presents a comprehensive outlook for the use of 3D-2D systems in solar cells. Finally, we investigate applications of 3D-2D systems beyond photovoltaics and offer our perspective on mixed-dimensional perovskite systems as semiconductor materials with unrivaled tunability, efficiency, and technologically relevant durability.
... On the other hand, the influence of balanced charge injection on recombination should be highlighted. The injected holes (or electrons) accumulated at the ETL/perovskite (or HTL/perovskite) interface will cause Auger recombination losses inevitably, resulting in a well-known issue, i.e., efficiency roll-off at high current density [113][114][115]. For example, the peak EQE of most visible PeLEDs was usually acquired under a low operational current density of below 10 mA cm −2 , in which the brightness was too low to be satisfactory for practical applications. ...
... On the other hand, the influence of balanced charge injection on recombination should be highlighted. The injected holes (or electrons) accumulated at the ETL/perovskite (or HTL/perovskite) interface will cause Auger recombination losses inevitably, resulting in a well-known issue, i.e., efficiency roll-off at high current density [113][114][115]. For example, the peak EQE of most visible PeLEDs was usually acquired under a low operational current density of below 10 mA cm −2 , in which the brightness was too low to be satisfactory for practical applications. ...
Manipulating the crystallization dynamics of perovskite emitters is an effective strategy for preparing high-performance perovskite light-emitting diodes (PeLEDs). In general, amorphous-like thermodynamically stable intermediates are desirable for a retarded and controllable crystallization process of perovskite emitters. Despite a variety of well-demonstrated strategies for crystallization control, it has been generally realized that perovskite thin-film emitters show problematic reproducibility. Here, we unraveled that the coordinating solvent vapor residues could raise deleterious influences on the formation of amorphous intermediate phases, which thus leads to varying crystal qualities from batch to batch. We demonstrated that undesirable crystalline intermediate phases tend to form with a strong coordination solvent vapor atmosphere, which alters the crystallization process and thus brings about additional ionic defects. By applying an inert gas flush strategy, this detrimental effect could be effectively mitigated, enabling PeLEDs with high reproducibility. This work provides new insight into the fabrication of efficient and reproducible perovskite optoelectronics.
... Due to the void in the inorganic framework is too small to accommodate the larger size organic amine cation, the inorganic layer of lead-halogen octahedra will be separated and forced to extend in certain directions, forming 2D and quasi-2D low-dimensional perovskites. And the combined effect of quantum confinement and dielectric restraint causes carrier recombination, which is due to the alternating stacking of organic and inorganic layers in the 2D perovskite, forming a natural quantum well structure (Fig. 1a) [47,48]. The 2D perovskites can be classified into three categories based on the orientation of the inorganic layer BX 6 octahedra (Fig. 1b); among them, the 2D perovskites with < 100 > orientation are the most diverse [36,49]. ...
Solar cells based on a three-dimensional (3D) crystalline perovskite framework exhibit desired photoconversion efficiency. However, 3D perovskites are prone to surface defects, leading to severe Shockley–Read–Hall (SRH) recombination and insufficient interactions between components, resulting in lower efficiency and stability. In contrast, two-dimensional (2D) perovskites have comparatively better excellent stability in hot and humid environments but suffer from lower efficiency. Recently, researchers reported that surface passivation of 3D perovskite by 2D perovskite improves the stability of solar cells without compromising their efficiency. In this review, the recent advances in surface modification of three-dimensional perovskites using two-dimensional perovskites are discussed. The crystal structures, photoelectric properties, and surface passivation strategies of 2D/3D perovskite solar cells with different components are systematically presented. Finally, the prospect of using two-dimensional perovskite passivation technology to further improve photovoltaic performance is discussed.
