High-Performance Blue Quasi-2D Perovskite Light-Emitting Diodes via Balanced Carrier Confinement and Transfer

Extensive investigation of the passivating agents has been performed to suppress the perovskite defects.However,very few attentions have been paid to rationally design the passivating agents for the balance of the carrier confinement and transfer in quasi-2D perovskites,which is essential to achieve high-performance perovskite LEDs(PeLEDs).In this work,tributylphosphine oxide(TBPO)with moderate carbon chain length is demonstrated as a decent passivator for the quasi-2D perovskites by strengthening the carrier confinement for massive radiative recombination within the perovskites,and more importantly providing efficient carrier transfer in the quasi-2D perovskites.Benefiting from these interesting optoelectronic properties of TBPO-incorporated perovskites,we achieve high-efficient blue PeLEDs with an external quantum efficiency up to 11.5%and operational stability as long as 41.1 min without any shift of the electroluminescence spectra.Consequently,this work contributes an effective approach to promote the carrier confinement and transfer for high-performance and stable blue PeLEDs.

Performance and stability-enhanced inorganic perovskite light-emitting devices by employing triton X-100

Significantly enhanced electroluminescence performance and stability of all-inorganic perovskite light-emitting devices(PeLEDs) have been achieved by adding triton X-100 into the perovskite precursors.The small perovskite grains arranged tightly and formed large grains as the triton X-100 were introduced.Thus the nonradiative defects originated from Pb atoms at the grain boundaries were highly passivated by triton X-100 and resulted in the promotion of PeLED performance,including a turn-on voltage of 3.2 V,a brightness of 63500 cd/m^(2),a current efficiency of 17.4 cd/A,and a prolonged lifetime of 2 h in air.

Directional emissions from perovskite nanocrystals thin film enabled by metasurface integration through one step spin-coating process

Advances in thin film light-emitting devices have fueled the rapid growth of a new class of solid-state lighting devices,featuring low fabrication cost,high quantum efficiency,broadband spectrum coverage,etc.In contrast to the conventional inorganic semiconductors that rely on lattice matched high crystalline quality substrate,solution processable thin films eliminate the dependence on the substrate,which is highly desired for the ease and versatility of integrations with foreign medium.By taking this advantage,this work developed an ultracompact solution to control the directionality of thin film emitters using integrated dielectric metasurface through one step spin-coating process.As a proof of concept,directional emissions from perovskite nanocrystal thin film,including collimated light emissions and two-dimensional beam steering,are experimentally demonstrated.Notably,our approach,where light emitters were integrated on the back side of substrate after the fabrication of metasurface,judiciously avoids any potential degradation of material optical quality caused by the multi-step nanofabrication.Therefore,it can serve as a generalized scheme to engage the advantageous properties of dielectric metasurface,including the compactness,high efficiency,beam controllability with the emerging thin film light-emitting diodes(LEDs),which is applicable to a wide range of solution processable materials,including organic light-emitting diodes,quantum-dot light emitting diodes,polymer LEDs,and perovskite LEDs,opening up new pathways to develop low-cost and ultra-compact solid state light sources with versatile beams characteristics.

Stable and high performance all-inorganic perovskite light-emitting diodes with anti-solvent treatment

Optoelectronic applications based on the perovskites always face challenges due to the inherent chemical composition volatility of perovskite precursors. The efficiency of perovskite-based light-emitting diodes(Pe-LEDs) can be enhanced by improving the perovskite film via solvent engineering. A dual solvent post-treatment strategy was applied to the perovskite film, which provides a synchronous effect of passivating surface imperfections and reduces exciton quenching, as evidenced by improved surface morphology and photoluminance. Thus, the optimized Pe-LEDs reach 17,866 cd · m-2 maximum brightness, 45.8 cd · A-1 current efficiency, 8.3% external quantum efficiency, and relatively low turn-on voltage of2.0 V. Herein, we present a simple technique for the fabrication of stable and efficient Pe-LEDs.

Morphology Engineering toward Highly Emissive Mn^(2+)Doped PEA_(2)PbBr_(4) Perovskite with Their LED Application via Phosphonium Passivation

Mn^(2+)-doped lead halide perovskites either in 3D or 2D have been extensively explored due to their rich energy-transfer behaviors.While their application on LED is still lagging behind in comparison to non-doped 3D perovskite due to inferior film-formation and low luminescent efficiency.Here we report an in-situ-formed Mn^(2+)doped 2D perovskite nanocrystal(NCs)film by introducing quaternary phosphonium salt during the crystallizing process.The as-formed film shows improved luminescent efficiency with emission peaked at 600 nm and photo-luminescence quantum yield(PLQY)of as high as 73.37%,which is about 1.3 times higher than that of pristine film.Further characterizations confirm the enhanced confinement effect from smaller size particle is responsible for the improved luminescent efficiency.The perovskite LEDs based on pristine and phosphonium passivated thin films were fabricated,and a great improvement in the external quantum efficiency of these LEDs(from 0.0017%to 0.12%)is observed due to the improved morphology and enhanced luminescent efficiency.

Two-dimensional materials for light emitting applications:Achievement,challenge and future perspectives

The two-dimensional(2D)materials have been widely developed recently in material characteristics with advanced optical and electrical properties,and they have been extensively studied as candidates for the next generation of optoelectronic devices.This review will mainly focus on the preparation methods and the light emitting applications of 2D transition metal dichalcogenides(TMDs),2D black phosphorene(BP)and 2D perovskites.The review will first introduce the preparation methods for TMDs and BP.Due to the variations of band structure,exciton binding energies and light-matter interaction in TMDs and BP,the different light emitting devices(LEDs)designs based on TMDs and BP will be discussed and summarized.Then the review will turn the focus to 2D perovskites,starting with a description of the preparation methods for the different structural perovskites.In order to review and summarize the achievements of 2D perovskites-based LEDs,the high efficiency perovskites LEDs are discussed.Finally,the review will present challenges,opportunities,and outlook for the future development of 2D materials-based light emitting applications.