Polymer-Assisted In Situ Growth of All-Inorganic Perovskite Nanocrystal Film for Efficient and Stable Pure-Red Light-Emitting Devices

Abstract

In the past few years, substantial progress has been made in perovskite light-emitting devices. Both pure green and infrared thin-film perovskite light-emitting devices with external quantum efficiency over 20% have been successfully achieved. However, pure-red and blue thin-film perovskite light-emitting diodes still suffer from inferior efficiency. Therefore, the development of efficient and stable thin-film perovskite light-emitting diodes with pure-red and blue emissions is urgently needed for possible applications as a new display technology and solid-state lighting. Here, we demonstrate an efficient light-emitting diode with pure-red emission based on polymer-assisted in situ growth of highquality all-inorganic CsPbBr 0.6 I 2.4 perovskite nanocrystal films with homogenous distribution of nanocrystals with size 20−30 nm. With this method, we can dramatically reduce the formation temperature of CsPbBr 0.6 I 2.4 and stabilize its perovskite phase. Eventually, we successfully demonstrate a pure-red-emission perovskite light-emitting diode with a high external quantum efficiency of 6.55% and luminance of 338 cd/m 2 . Furthermore, the device obtains an ultralow turn-on voltage of 1.5 V and a half-lifetime of over 0.5 h at a high initial luminance of 300 cd/m 2 .

Sodium Ion Modifying In Situ Fabricated CsPbBr3 Nanoparticles for Efficient Perovskite Light Emitting Diodes

“…The XPS spectra in Figure S1a (Supporting Information) demonstrates the presence of the element Cs, Pb, Br, N and O, which implies the presence of PEA and PEO, and the XPS spectra of Pb4f in Figure S1b (Supporting Information) at 138.4 and 143.2 eV are attributed to Pb4f 7/2 and Pb4f 5/2 levels of Pb–Br, besides there exist two additional peaks at 136.3 and 141.2 eV whether NaBr is added or not, which indicates the peaks are not caused by the addition of NaBr. According to previous research, they are derived from the coordination between the O atom in PEO and Pb 2+ in CsPbBr 3 which proves the previous conjecture of the role of PEO . The XPS spectra of Na1s indicates the presence of Na + in NaBr modified CsPbBr 3 NPs (Figure b).…”

“…The longer PL lifetime of CsPbBr 3 NPs with NaBr modifying represents the better defect passivation and suppression of the defect‐assisted nonradiative recombination . To further confirm the better defect passivation of CsPbBr 3 NPs with NaBr modifying, the photoluminescence quantum yield (Figure f) and trap density extraction by dark current–voltage measurement of the hole‐only device (Figure S2, Supporting Information) with the device structure of ITO/poly(ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS)/CsPbBr 3 NPs/Au are taken . As 5% NaBr is added, the PLQY of CsPbBr 3 NPs is enhanced from 38% ± 5% to 68% ± 5%, and the onset voltage of the trap‐filled limit (TFL) regime ( V TFL ) debases from 0.94 to 0.59 V. Both results manifest that the defects of CsPbBr 3 NPs are better passivated by the modifying of NaBr, which may be attributed to that the smaller size of Na + provides a greater chance to fill up the surface vacancies in NPs.…”

Highly Photoluminescent and Environmentally Stable Perovskite Nanocrystals Templated in Thin Self‐Assembled Block Copolymer Films

“…The binding energy of Pb 4f was clearly changed with the incorporation of PS‐ b ‐P2VP with MAPbBr 3 crystals while the state of Br atoms was unchanged. Two characteristic peaks were appeared at 137 and 141.8 eV which corresponded to the energies of the Pb atoms in the surface of MAPbBr 3 crystals bonded with N atoms of pyridine rings of P2VP blocks . It should be noted that the intermediate crystals of 3D perovskite‐like crystal structures typically observed in the adducts with dimethyl sulfoxide could not be observed.…”

Improving Stability of Cesium Lead Iodide Perovskite Nanocrystals by Solution Surface Treatments

“… 8 In the field of LEDs, there have been demonstrations of high-purity yellow LEDs lasting for 1 h, 9 white LEDs, 10 , 11 and CsPbX 3 red-emitting films. 12 , 13 Moreover, the emission spectra can be modulated in a variety of ways, such as precipitation temperature, 14 halogen-doped anion exchange, 15 and amount of capping molecules. 16 , 17 In addition, CsPbX 3 has a narrow emission peak width and good thermal stability, which make them attractive candidates for future optoelectronic applications.…”