A Multifunctional “Halide‐Equivalent” Anion Enabling Efficient CsPb(Br/I)₃ Nanocrystals Pure‐Red Light‐Emitting Diodes with External Quantum Efficiency Exceeding 23%

Abstract

Pure‐red perovskite LEDs (PeLEDs) based on CsPb(Br/I)3 nanocrystals (NCs) usually suffer from a compromise in emission efficiency and spectral stability on account of the surface halide vacancies‐induced nonradiative recombination loss, halide phase segregation, and self‐doping effect. Herein, a “halide‐equivalent” anion of benzenesulfonate (BS–) is introduced into CsPb(Br/I)3 NCs as multifunctional additive to simultaneously address the above challenging issues. Joint experiment‐theory characterizations reveal that the BS– can not only passivate the uncoordinated Pb2+‐related defects at the surface of NCs, but also increase the formation energy of halide vacancies. Moreover, because of the strong electron‐withdrawing property of sulfonate group, electrons are expected to transfer from the CsPb(Br/I)3 NC to BS– for reducing the self‐doping effect and altering the n‐type behavior of CsPb(Br/I)3 NCs to near ambipolarity. Eventually, synergistic boost in device performance is achieved for pure‐red PeLEDs with CIE coordinates of (0.70, 0.30) and a champion external quantum efficiency of 23.5%, which is one of the best value among the ever‐reported red PeLEDs approaching to the Rec. 2020 red primary color. Moreover, the BS–‐modified PeLED exhibits negligible wavelength shift under different operating voltages. This strategy paves an efficient way for improving the efficiency and stability of pure‐red PeLEDs.

Suppressing Ion Migration of Mixed‐Halide Perovskite Quantum Dots for High Efficiency Pure‐Red Light‐Emitting Diodes

“…Additionally, the EQE of the PeLED shows a low rolloff with increasing brightness: for luminance's of 380 and 935 cd m −2 , the corresponding EQEs are 14.5% and 10.4%, respectively. Display applications typically require a luminance of ≈400 cd m −2 or higher [6] and at this output our device exceeds all reported mixed halide PeLEDs of the maximum EQE of over 20%, [2,17,24,32] which is significant for high-definition display applications (Table S3, Supporting Information). In order to explored the reason of the low rolloff of the PeLED based on CPIBr-D+T QDs, we obtain the PLQY of the CPIBr and CPIBr-D+T QDs with the change of excitation light intensity.…”

Cubic CsPbI3 Nanoarchitectonics with High and Stable Photoluminescence toward White Light-Emitting Diodes

“…Cesium lead halide (CsPbX 3 ) perovskite nanocrystals (NCs) are widely applied in the fields of solar cells, photodetectors, liquid crystal televisions, and other optoelectronics − due to their high photoluminescence quantum yields (PLQYs), , narrow spectral widths, tunable PL spectrum in the whole visible light region, adjustable band gaps, and high color purity. − In addition, low-dimensional perovskite NCs have been continuously studied. , However, the surface ligands of these NCs are easily desorbed during the purification process, resulting in the aggregation and growth of NCs into large particles, which decreases the stability and PLQYs . In particular, cesium lead iodide (CsPbI 3 ) NCs can accelerate degradation under the conditions of water, heat, and strong light.…”

Uniform nucleation and growth of Cs3Cu2I5nanocrystals with high luminous efficiency and structural stability and their application in white light-emitting diodes

“…[1][2][3][4][5][6][7][8][9][10][11][12][13] To date, the external quantum efficiencies (EQEs) of perovskite-based LEDs have exceeded over 20%, showing great potential in next-generation displays and lighting. [14][15][16][17][18][19][20] However, their intrinsic heavy-metal toxicity and instability seriously restrict their practical application. [21][22][23][24] Recently, copper(I)-based halide Cs 3 Cu 2 I 5 NCs have emerged as a promising substitute for lead halides due to their relatively low toxicity, Earth-abundant composition and unique optoelectronic properties, such as high emission stability, low self-absorption and self-trapped exciton (STE) emission.…”