RESUMEN
Blue light-emittin g diodes (LEDs) are important components for perovskite electroluminescence applications, which still suffer from insufficient luminescence efficiency and poor stability. In Cl/Br mixed perovskite NCs, surficial defects cause severe light failure and ion migration, the in-depth mechanism of which is also not clear. To gain insights into these issues, we employ the ligand post-addition approach for mixed Cl/Br NCs by using octylammonium hydrobromide (OctBr) ligands, which effectively decrease surficial light loss and block ion migration pathways. The passivated CsPbCl1.5Br1.5 NCs exhibit exceptional blue emission with 95% PLQY, and the electroluminescence spectra of LEDs are located at the initial positions at the initial states. The treated NC blue devices show a negligible color shift as the voltage increases, which proves that electric-field-driven ion migration is drastically suppressed. In addition, OctBr-treated CsPbCl1.5Br1.5 and CsPbClBr2 NC LEDs show high external quantum efficiencies of 2.42 and 3.05% for emission peaks at 456 and 480 nm, respectively. Our work identified the nature of NC surface defects and provided a surficial modification approach to develop high-performance and color-stable blue mixed-halide perovskite LEDs.
RESUMEN
Achieving high efficiency and stable pure blue colloidal perovskite quantum dot (QD) light-emitting diodes (LEDs) is still an enormous challenge because blue emitters typically exhibit high defect density, low photoluminescence quantum yield (PLQY) and easy phase dissociation. Herein, an organic cation composition modification strategy is used to synthesize high-performance pure blue perovskite quantum dots at room temperature. The synthesized FA-CsPb(Cl0.5Br0.5)3 QDs show a bright photoluminescence with a high PLQY (65%), which is 6 times higher than the undoped samples. In addition, the photophysical properties of the FA cation doping was deeply illustrated through carrier dynamics and first principal calculation, which show lower defects, longer lifetime, and more reasonable band gap structure than undoped emitters. Consequently, pure blue FA-CsPb(Cl0.5Br0.5)3 QDs light-emitting devices were fabricated and presented a maximum luminance of 1452 cd m-2, and an external quantum efficiency of 5.01 % with an emission at 474 nm. The excellent photoelectric properties mainly originate from the enhanced blue QDs emitter and effective charge injection and exciton radiation. Our finding underscores this easy and feasible room temperature doping approach as an alternative strategy to blue perovskite QD LED development.
RESUMEN
Ligands on the surface of perovskite nanocrystals are important to stabilize the nanocrystal structure. However, the research of ligands on Mn2+ ion-doped CsPbCl3 nanocrystals (Mn: CsPbCl3 NCs), a promising candidate family for the lightning community, is relatively rare. Here, we demonstrate a new ligand modification strategy for preparing high-quality Mn: CsPbCl3 NCs by a simple hot-injection method. Thiophene derivative, for the first time, is applied as ligands for perovskite nanocrystals. The new ligands of thiophene derivatives passivate defects on the surface of NCs and enhance optical properties, originating from the sulfur in thiophene additives binding to the uncoordinated lead ions. The photoluminescence quantum yield of the modified Mn: CsPbCl3 NCs is 93% in comparison with 46% of the pristine counterparts, whose value is the highest to date for ligand-modified Mn: CsPbCl3 NCs. Meanwhile, the thermal, storage, and purification stability are also significantly improved. The performance of related LEDs is also investigated.
RESUMEN
Light-emitting diodes using metal halide perovskite (PeLEDs) exhibit a strong potential for emerging display technologies due to their unique optoelectronic characteristics. However, for blue emission PeLEDs, there remains a huge challenge to achieve high performance, an issue that has been addressed in their red and green counterparts. The community is circumventing the challenges in synthesizing stable, high-quantum-efficiency, and low-defect-density blue emitters. Here, a facile strategy that replaces Pb by adding a monovalent ion Cu+, in this case into CsPbClBr2 perovskite, is carried out. This decreases the Pb dangling bonds and increases the radiative recombination for the enhancement of blue emission. The nanoparticles obtained by this method maintain a blue emission at 479 nm. The photoluminescence quantum yield is 2 times higher than the pristine analogue. The corresponding perovskite nanocrystal (PNC) LEDs achieve stable electroluminescence spectrum at high brightness. Simultaneously, the optimal blue PNC LEDs obtain the maximum values of luminance and external quantum efficiency of 1537 cd m-2 and 3.78%, respectively. And the device realizes typical blue light CIE chromaticity coordinates of (0.098, 0.123). Our work reveals that the substitution of Pb by heterovalent ions significantly decreases nanocrystal defects, which will pave the way of perovskite LEDs for practical applications in the future.
