Highly efficient Cs-based perovskite light-emitting diodes enabled by energy funnelling

118

Lead halide perovskite quantum dots (PQDs) have been widely recognized as highly luminescent materials for efficient optoelectronic applications owing to their fascinating electronic and optical properties. In spite of the excellent performances for the fabrication of lighting devices, the poor chemical instability greatly hampers their practical applications. The inevitable ion exchange and degradation driven from light, moisture, heat, and others limits their applications such as solid‐state light‐emitting diodes (LEDs). In this paper, the stability of PQDs is improved by integrating them in CaF2 hierarchical nanospheres (HNSs). In comparison with the pristine perovskite materials, the outstanding optical performances are well preserved. The perovskite displays a unique quantum confinement effect in the HNSs. Additionally, embedding the quantum dots in robust CaF2 matrices protects them from being damaged by moisture or light irradiation as well as anion exchange. Furthermore, white LED devices are obtained by mixing green CaF2‐CsPbBr3 composites and commercial red phosphors on a blue chip. The optimized devices show a high luminous efficacy of 62.7 lm W–1 under 20 mA current and preserve the value of 56.3 lm W–1 after working for 8 h.

Section: Introductionmentioning

confidence: 99%

Highly Luminescent Lead Halide Perovskite Quantum Dots in Hierarchical CaF₂ Matrices with Enhanced Stability as Phosphors for White Light‐Emitting Diodes

Wei

Xiao

Xie

et al. 2018

118

“…To overcome this limitation, an effective strategy is to reduce the grain size in perovskite films to spatially confine the charge carriers for the enhancement of radiative monomolecular (excitonic) recombination . In addition, 2D Ruddlesden‐Popper perovskites with layered structures have been developed recently by intercalating large organic counter‐cations within the lead halide networks, leading to higher PL efficiency due to enlarged exciton binding energy and concentrated charge carriers . For instance, phenethylammonium bromide (PEABr) has been incorporated to form mixed‐dimensional CsPbBr 3 perovskites, which can facilitate the radiative recombination along with higher PLQYs and improved device performance in PeLEDs due to efficient energy funneling from larger bandgap (2D) domains to the lowest bandgap (3D) radiative domains .…”

Section: Introductionmentioning

confidence: 99%

Efficient CsPbBr₃ Perovskite Light‐Emitting Diodes Enabled by Synergetic Morphology Control

Cheng

Huang

Shen

et al. 2018

133

The development of solution‐processed inorganic metal halide perovskite light‐emitting diodes (PeLEDs) is currently hindered by low emission efficiency due to morphological defects and severe non‐radiative recombination in all‐inorganic perovskite emitters. Herein, bright PeLEDs are demonstrated by synergetic morphology control over cesium lead bromide (CsPbBr3) perovskite films with the combination of two additives. The phenethylammonium bromide additive enables the formation of mixed‐dimensional CsPbBr3 perovskites featuring the reduced grain size (<15 nm) and efficient energy funneling, while the dielectric polyethyleneglycol additive promotes the formation of highly compact and pinhole‐free perovskite films with defect passivation at grain boundaries. Consequently, green PeLEDs achieve a current efficiency of 37.14 cd A−1 and an external quantum efficiency of 13.14% with the maximum brightness up to 45 990 cd m−2 and high color purity. Furthermore, this method can be effectively extended to realize flexible PeLEDs on plastic substrates with a high efficiency of 31.0 cd A−1.

“…In the case of BABr:PbBr 2 = 1:10, the addition of BABr reduces the perovskite grains to tens of nanometers, and also results in a smoother surface compared to pure 3D FAPbBr 3 film (Figure b,f). This is explained by the fact that bulky ligands like BABr can restrict the grain growth by capping at the surface of the 3D crystallites . As is also indicated by UV–vis and XRD measurements, this film contains significantly less 2D perovskite components.…”

Section: Resultsmentioning

confidence: 77%

Exploiting Two‐Step Processed Mixed 2D/3D Perovskites for Bright Green Light Emitting Diodes

Yan

Croes

Fakharuddin

et al. 2019

Mixed 2D/3D perovskite films with self‐assembled quantum wells have significantly improved the performance of perovskite light emitting diodes (PeLEDs). In this work, such films are fabricated through a two‐step interdiffusion method that is widely employed in processing of perovskite solar cells, however, remains rarely explored for PeLEDs. The effects of incorporating large‐cation ligand, i.e., butylammonium bromide (BABr) into formamidinium lead bromide (FAPbBr3) based perovskites, in terms of film composition, morphology, optoelectronic properties as well as device performance are thoroughly investigated in this method. By modulating BABr:PbBr2 ratio in the precursor solution, the optimal device shows a maximum external quantum efficiency (EQE) of 7.36% at 147.7 mA cm−2 and a brightness of 37 720 Cd m−2 at 5 V. The performance is remarkably higher than a reference device without BABr that shows a maximum EQE of 2.53% and a brightness of 6190 Cd m−2 at 5 V. The versatility of this method is further extended to another large‐cation ligand, 4‐fluoro‐benzylammonium bromide (F‐BZABr), which leads to maximum EQE of 8.55%. This work indicates two‐step processed mixed 2D/3D perovskites are promising for bright green PeLEDs.