Continuous-Wave Lasing in Perovskite LEDs with an Integrated Distributed Feedback Resonator.

Realization of electrically pumped laser diodes based on solution-processed semiconductors is a long-standing challenge. Metal halide perovskites have shown great potential toward this goal due to their excellent optoelectronic properties. Continuous-wave (CW) optically pumped lasing in a real electroluminescent device represents a key step to current-injection laser diodes, but it has not yet been realized.

Indirect Bandgap Emission of the Metal Halide Perovskite FAPbI at Low Temperatures.

In this work, we provide a picture of the band structure of FAPbI by investigating low-temperature spin-related photophysics. When the temperature is lower than 120 K, two photoluminescence peaks can be observed. The lifetime of the newly emerged low-energy emission is much longer than that of the original high-energy one by two orders of magnitude.

Vapor-Assisted In Situ Recrystallization for Efficient Tin-Based Perovskite Light-Emitting Diodes.

Tin-based perovskites are a promising candidates to replace their toxic lead-based counterparts in optoelectronic applications, such as light-emitting diodes (LEDs). However, the development of tin perovskite LEDs is slow due to the challenge of obtaining high-quality tin perovskite films. Here, a vapor-assisted spin-coating method is developed to achieve high-quality tin perovskites and high-efficiency LEDs.

Molecularly Controlled Quantum Well Width Distribution and Optoelectronic Properties in Quasi-2D Perovskite Light-Emitting Diodes.

Owing to their excellent optoelectronic properties, quasi-2D perovskites with self-assembled multiple quantum well (MQW) structures have shown great potential in light-emitting diode (LED) applications. Understanding the correlation between the bulky cation, quantum well assembly, and optoelectronic properties of a quasi-2D perovskite is important. Here, we demonstrate that the dipole moment of the bulky cation can be one of the fundamental factors that controls the distribution and crystallinity of different quantum wells.

High-Brightness Perovskite Microcrystalline Light-Emitting Diodes.

Here a high-brightness perovskite microcrystalline light-emitting diode (LED) is reported, in which the perovskite microcrystals were grown directly on the conductive substrate and a simple metal-insulator-semiconductor structure was adopted. A peak external quantum efficiency of 0.46% was obtained, which is high for perovskite microcrystalline LEDs.

Efficient light-emitting diodes based on oriented perovskite nanoplatelets.

Solution-processed planar perovskite light-emitting diodes (LEDs) promise high-performance and cost-effective electroluminescent devices ideal for large-area display and lighting applications. Exploiting emission layers with high ratios of horizontal transition dipole moments (TDMs) is expected to boost the photon outcoupling of planar LEDs. However, LEDs based on anisotropic perovskite nanoemitters remain to be inefficient (external quantum efficiency, EQE <5%) due to the difficulties of simultaneously controlling the orientations of TDMs, achieving high photoluminescence quantum yields (PLQYs) and realizing charge balance in the films of assembled nanostructures.

Three-dimensional monolithic micro-LED display driven by atomically thin transistor matrix.

Two-dimensional materials are promising candidates for future electronics due to unmatched device performance at atomic limit and low-temperature heterogeneous integration. To adopt these emerging materials in computing and optoelectronic systems, back end of line (BEOL) integration with mainstream technologies is needed. Here, we show the integration of large-area MoS thin-film transistors (TFTs) with nitride micro light-emitting diodes (LEDs) through a BEOL process and demonstrate high-resolution displays.

Unveiling the additive-assisted oriented growth of perovskite crystallite for high performance light-emitting diodes.

Solution-processed metal halide perovskites have been recognized as one of the most promising semiconductors, with applications in light-emitting diodes (LEDs), solar cells and lasers. Various additives have been widely used in perovskite precursor solutions, aiming to improve the formed perovskite film quality through passivating defects and controlling the crystallinity. The additive's role of defect passivation has been intensively investigated, while a deep understanding of how additives influence the crystallization process of perovskites is lacking.

Efficient and bright warm-white electroluminescence from lead-free metal halides.

Solution-processed metal-halide perovskites are emerging as one of the most promising materials for displays, lighting and energy generation. Currently, the best-performing perovskite optoelectronic devices are based on lead halides and the lead toxicity severely restricts their practical applications. Moreover, efficient white electroluminescence from broadband-emission metal halides remains a challenge.

Perovskite Light-Emitting Diodes with Near Unit Internal Quantum Efficiency at Low Temperatures.

Room-temperature-high-efficiency light-emitting diodes based on metal halide perovskite FAPbI are shown to be able to work perfectly at low temperatures. A peak external quantum efficiency (EQE) of 32.8%, corresponding to an internal quantum efficiency of 100%, is achieved at 45 K.

In Situ-Fabricated Perovskite Nanocrystals for Deep-Blue Light-Emitting Diodes.

Efficient and stable deep-blue emission from perovskite light-emitting diodes (LEDs) is required for their application in lighting and displays. However, this is difficult to achieve due to the phase segregation issue of mixed halide perovskites and the challenge of synthesizing high-quality single-halide deep-blue perovskite nanocrystals through a traditional method. Here, we show that an antisolvent treatment can facilitate the in situ formation of perovskite nanocrystals using a facile spin-coating method.

Intermediate-phase-assisted low-temperature formation of γ-CsPbI films for high-efficiency deep-red light-emitting devices.

Black phase CsPbI is attractive for optoelectronic devices, while usually it has a high formation energy and requires an annealing temperature of above 300 °C. The formation energy can be significantly reduced by adding HI in the precursor. However, the resulting films are not suitable for light-emitting applications due to the high trap densities and low photoluminescence quantum efficiencies, and the low temperature formation mechanism is not well understood yet.

Surface-Plasmon-Enhanced Perovskite Light-Emitting Diodes.

Perovskite light-emitting diodes (PeLEDs) have attracted considerable attention because of their potential in display and lighting applications. To promote commercialization of PeLEDs, it is important to improve the external quantum efficiency of the devices, which depends on their internal quantum efficiency (IQE) and light extraction efficiency. Optical simulations have revealed that 20-50% of the light generated in the device will be lost to surface plasmon (SP) modes formed in the metal/dielectric interfaces.

High-Performance Perovskite Light-Emitting Diode with Enhanced Operational Stability Using Lithium Halide Passivation.

Defect passivation has been demonstrated to be effective in improving the radiative recombination of charge carriers in perovskites, and consequently, the device performance of the resultant perovskite light-emitting diodes (LEDs). State-of-the-art useful passivation agents in perovskite LEDs are mostly organic chelating molecules that, however, simultaneously sacrifice the charge-transport properties and thermal stability of the resultant perovskite emissive layers, thereby deteriorating performance, and especially the operational stability of the devices. We demonstrate that lithium halides can efficiently passivate the defects generated by halide vacancies and reduce trap state density, thereby suppressing ion migration in perovskite films.

Tin-Based Multiple Quantum Well Perovskites for Light-Emitting Diodes with Improved Stability.

Tin-based halide perovskites have attracted considerable attention for nontoxic perovskite light-emitting diodes (PeLEDs), but the easy oxidation of Sn and nonuniform film morphology cause poor device stability and reproducibility. Herein, we report a facile approach to achieve efficient and stable lead-free PeLEDs by using tin-based perovskite multiple quantum wells (MQWs) for the first time. On the basis of various spectroscopic investigations, we find that the MQW structure not only facilitates the formation of uniform and highly emissive perovskite films but also suppresses the oxidation of Sn cations.