Recently, Professor Wei Zhibao, the OC University of OC, and Professor, Nangang University of Technology, Nanyang University of Technology, and Professor, University of Toronto, Canada, have made a major breakthrough in the study of perovskite lighting diodes.
The researchers utilizes the component distribution regulatory strategy of calcium and titanium to obtain a perovskite film excellent in flat and photoelectric properties, and improves the imbalance of electronic holes by adding a barrier layer to obtain external quantum efficiency of the perovskite light emitting diode ( EQE more than 20%, refreshed the highest record of the world of perovskite, while the stability is greatly improved, far exceeding international peers.
Related research results were published in the International Top Academic Journal Nature (DOL: 10.1038 / S41586-018-0575-3).
Introduction to results
Perovskite field of solar cell semiconductor material has achieved great success, organic - inorganic hybrid perovskite photoelectric conversion efficiency of the solar cell (PCE) has 3.8% from the initial authentication to the current efficiency of 23.3%. Due to the preparation cost of perovskite materials, the solution method is prepared, the fluorescent quantum is high, the color purity is high, and the color adjustable characteristics, the perovskite material is extremely potential in planar display and solid lighting. Since 2014, Richard H. Friend and Zhi-Kuang Tan, etc., the first-time perovskite light-emitting diode that can operate at room temperature, with MapBI3-X and MapBBBR3 (MA = CH3NH3 +) as a light-emitting layer of near-infrared light and green light The perovskite LED measured EQE was 0.76%, 0.1%, respectively.
Since then, the perovskite LED has attracted more and more researchers to invest research and have achieved continuous breakthroughs. However, the currently reported green light and red-photooladium ore LED is 14.36% and 11.7%, respectively, and the perovskite LED device is poor, far below the commercially available organic light emitting diode ( OLEDS and inorganic quantum dot light emitting diodes (EQE: 25% or more), etc. The perovskite LED has a large lifting space in efficiency and stability.
In this study, the researchers used CSPBBBR3 and MABR (MA = CH3NH3 +) in the solubility difference between polar solvent DMSO, by adding MABR additives in CSPBBR3 perovskite precursor, and accurately regulates the amount of MABR of the additive. The component distribution regulation of the calcium titanium mineral layer is successfully realized, and the surface is flat and dense, and the photoelectric performance has excellent perovskite film, and the device EQE exceeds 17%.
Through comparative pure electron and pure cavity devices, researchers found that electrons and hole injection imbalances in devices, excessive electron injection constrained further improvement of device performance, in turn, the researchers passed between the light-emitting layer and the electron transport layer Polymethyl methacrylate (PMMA) insulating material blocks the injection of excess electrons, improves the imbalance of electrons and holes in the device, further improving the efficiency of the device, and finally obtains EQE more than 20%, stability exceeds Perovite LED devices in 100 hours (T50> 100H), far exceeding international peers.
Profile
Figure of an optical characterization of different perovskite
(A) CSPBBR3, MAPBBBBBBBBBBBBBBBBBR3, mixed calcium ore 1.0 in fluorescent lamp and UV lamp;
(B) ultraviolet visible absorption curve of CSPBBBR3 and perovskite in different mixing ratios;
(C) CSPBBR3, MAPBBBBBR3, mixed calcium ore 1.0 PL curve (excitation wavelength 400 nm, 4uW) (D) CSPBBR3, MAPBBBR3, a fluorescence lane of mixed calcium ore 1.0.
Figure 2 component distribution regulates the increase of perovanium mineral layers
(A) a schematic view of a different composition distribution: single CsPbBr3, laminated CsPbBr3 / MABr and CsPbBr3 @ MABr core-shell structure;
(B) Plotes of PL under different perovskite in the ultraviolet lamp;
(C) Deep analysis of secondary ion mass spectrometry (SIMS) CSPBBR3 @ MABR nuclear shell structure;
(D) Focus ion beam (FIB) cutting, surface sputter C as a protective layer CSPBBR3 @ mabR shell nuclear structure TEM cross-section (in the figure shows that there is a MABR shell-shaped wrap CSPBBR3 grain).
Figure triacium-titanite LED device and performance characterization
(A) Schematic diagram of perovskite LED device, PEDOT: PSS and B3PYMPM are respectively used as holes transport layers (HTL) and electron transport layers (ETL);
(B) Working diagram of perovskite LED device;
(C) CE-V curves of devices of CSPBBR3, MAPBBBR3 and mixed calcium ore 1.0 as a light-emitting layer;
(D) J-V curves of pure electron pure void devices of CSPBBR3 and mixed perovskitanium 1.0;
(E) Current efficiency distribution statistics of the device;
(F) The best performance of the EQE-V curve of mixed calcium ore 1.0.
Figure tetra-calcium ore layer and electron transport layer insertion of PMMA barrier layers further increase device performance
(A) Pure electron pure void device J-V curve of the PMMA barrier layer in the perovskite layer and the electron transport layer;
(B) Schematic structural diagram of the device inserted into the PMMA barrier layer in the perovskite layer and the electron transport layer;
(C) Insert the current efficiency distribution statistics of the device after the PMMA barrier layer; the optimal perovskite LED
(D) L-J-V curve and (e) EQE-L curve;
(F) Perovskite LED life test curve.
summary
The researchers use CSPBBR3 and MABR in the solubility difference between polar solvent DMSO, and successfully coated with a high fluorescent quantum efficiency (PLQY) having a CSPBBBBR3 @ MABR core shell structure with a perovskite film. The study pointed out that the addition of MABR helps CSPBBR3's necronomic and greater, and effectively passivate CSPBBR3 surface defects, reducing radiation composite, and the MABR on CSPBBR3 can act as a balanced charge injection.
Through the insertion of PMMA insulating materials between the light-emitting layer and the electron transport layer, the researchers further improve the equilibrium of electronic hole injection in the device, and finally obtained perovskite luminous secondary tube EQE reached 20.3%, stability for more than 100 hours. The development of perovskite LEDs has reached a new height. , Read the full text, original title: external quantum efficiency of the perovskite LED exceeds 20%, once again refreshes the world record
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