Highly stable CsPbBr₃ quantum dots coated with alkyl phosphate for white light-emitting diodes

Abstract

Inorganic halide perovskite quantum dots (QDs) suffer from problems related to poor water stability and poor thermal stability. Here we developed a simple strategy to synthesize alkyl phosphate (TDPA) coated CsPbBr QDs by using 1-tetradecylphosphonic acid both as the ligand for the CsPbBr QDs and as the precursor for the formation of alkyl phosphate. These QDs not only retain a high photoluminescence quantum yield (PLQY, 68%) and narrow band emission (FHWM ∼ 22 nm) but also exhibit high stability against water and heat. The relative PL intensity of the QDs was maintained at 75% or 59% after being dispersed in water for 5 h or heated to 375 K (100 °C), respectively. Finally, white light-emitting diodes (WLEDs) with a high luminous efficiency of 63 lm W and a wide color gamut (122% of NTSC) were fabricated by using green-emitting CsPbBr/TDPA QDs and red-emitting KSiF:Mn phosphors as color converters. The luminous efficiency of the WLEDs remained at 90% after working under a relative humidity (RH) of 60% for 15 h, thereby showing promise for use as backlight devices in LCDs.

Synergistic Surface Passivation of CH3NH3PbBr3 Perovskite Quantum Dots with Phosphonic Acid and (3‐Aminopropyl)triethoxysilane

“…[27] The O1 sspectrum (Figure 6a)f or PQD MPA could be fitted with three peaks:N ÀO at 532.9 eV, [28] P=Oa t5 31.3 eV, [29] and PÀOÀPb at 530.8 eV. [12] The N1ss pectrum (Figure 6b)f or PQD MPA could be fitted with three peaks: ÀNH 3 + at 401.5 eV, [30] CÀNa t4 01.2 eV, [31] ÀNH 2 at 399.7 eV, [30b-d] andN ÀOa t3 99.0 eV. [28,32] Figure 6c shows the Pb 4f spectrum of the samples of PQD MPA ,P QD HPA ,P QD TDPA , Figure 5.…”

“…XPS spectra revealed the presence of PA and APTES ligands in PQDs and their interaction. Specifically,t he XPS spectras how the presence of the NÀOp eak at 532.9 eV [28] and PÀOÀPb peak at 530.80 eV [12] in O1 s, with the ÀNH 3 + peak at 401.50eV, [30] the ÀNH 2 peak at 399.7 eV, [30b-d] and the NÀO peak at 399.0 eV [28,32] As illustrated in Figure 8, at least three types of surface defect sites are expected for the PQDs:M A + ,P b 2 + ,a nd X À . Therefore, we need am inimum of three ligands to effectively passivate them.…”

“…[11] In another report, alkyl phosphate coated CsPbBr 3 PQDs not only improved stabilitya gainst water and heat, but also demonstrated the potential to be used in LED fabrication. [12] Similarly,c onventional carboxylate and ammonium capping ligands (oleic acid and oleylamine, respectively) can be replaced with octylphosphonic acid or zwitterionic long-chain molecules( such as phosphocholine) to enhance the durability and stability of CsPbX 3 nanocrystals. [13] Furthermore, PA w-ammonium chlorides have been shown to passivate the Pb 2 + and I À surfaced efects of CH 3 NH 3 PbI 3 ,a nd the associated solar cell shows good PV performance and moisture stability.…”

Single Halide Perovskite/Semiconductor Core/Shell Quantum Dots with Ultrastability and Nonblinking Properties

“…stability, such as by introducing mesoporous silica, [11] intermolecular CC bonding, [12] alkyl phosphate layer, [13] chemical doping, [14] and heterostructures, such as CsPbBr 3 /ZnS heterodimers and CH 3 NH 2 PbX 3 /SiO 2 sphere. [15,16] Also, these materials usually exhibit obvious photoluminescence (PL) blinking at the single-dot level, [15] which is caused by the nonradiative Auger recombination process [17] and has severe detrimental effects on the efficiency of optoelectronic devices based on spontaneous emission (such as LEDs).…”

Near UV-pumped yellow-emitting Sr9MgLi(PO4)7:Eu2+ phosphor for white-light LEDs

“…However, the lacking of red spectral contribution in YAG:Ce 3+ phosphors leads to a poor color-rendering index (R a <75) and a high correlated color temperature (CCT>7,000 K) [9,10]. To compensate the lacking of red components, red-emitting phosphors or quantum dots have been studied and applied in WLEDs, such as K 2 SiF 6 :Mn 4+ phosphors and CsPbBr 3 quantum dots [11,12]. Another alternative way to overcome those disadvantages is to combine the near-ultraviolet (n-UV) LED chip with blue and yellow phosphors [4].…”