Colloidal cesium lead bromide-based anisotropic nanorods for improving outcoupling in perovskite light-emitting diodes

Figures & data

Scheme 1. The schematic illustration of the chemical transformation of Cs₄PbBr₆ into CsPbBr₃ nanorods due to ligand-regulated reactions at the water-oil interface. The bottom is the images of Cs₄PbBr₆ NCs to the intermediate stage (oil-water ligand modulation) to CsPbBr₃ nanorods.

Figure 1. (a) Field-emission transmission electron microscope (FE-TEM) image, (b-c) the histogram of the average length and width of the CsPbBr₃ nanorod for 44 h of ligand-modification times, (d) FE-TEM image, (e-f) the histogram of the average length and width of the nanorods for 33 h of ligand modification times, (g) FE-TEM image, and (h-i) the histogram of the average length and width of the nanorod for 22 h of ligand modification times.

Figure 2. (a) XRD pattern of nanopolyhedrons Cs₄PbBr₆ NCs and CsPbBr₃ nanorods (mixed phase and final nanorods). Enlarged XRD pattern of (b) (100) crystal plane, (c) (110) crystal plane, (d) (200) crystal plane, (e) (210) crystal plane, and (f) (211) crystal plane of Cs₄PbBr₆ NCs and CsPbBr₃ nanorods (mixed phase and final nanorods). (g) PLQY as a function of different ligand-modification times (0, 11, 22, 33, 44, and 55 hr), and (h) the absorption and photoluminescent (PL) spectra of CsPbBr₃ nanorods (44 hr).

Figure 3. (a) XPS spectra of CsPbBr₃ nanorods film. High-resolution XPS spectra of (b) Cs 3d, (c) Pb 4f, and (d) Br 3d of nanorods.

Figure 4. (a) Angle-dependent photoluminescence intensity of the nanorods, where isotropic (red) and perfect horizontal (blue) orientation cases are added for comparison; and (b) refractive index (n) and extinction coefficient (k) of the thin film of anisotropic nanorods

Figure 5. (a) The energy level diagram of functional layers in PeLEDs, (b-c) schematic illustration and cross-sectional TEM images of PeLEDs, (d) current density-voltage-luminance characteristics, (e) external quantum efficiency vs. current density curve, (f-g) histogram of maximum external quantum efficiency and luminance values. (h-i) current efficiency-power efficiency vs. current density, and EL spectra of ANR-LEDs. The inset of Figure 5(i) is the operation image of the LED under 4.8 V.

Table 1. Comparison of optoelectronic properties of PeLEDs based on CsPbBr₃.

Device Configuration	J (mA/cm^2)	Lmax (cd/m^2)	CE (cd/A)	EQE (%)	Ref.
ITO/PEDOT: PSS/P-TPD/CsPbBr3 Nanorods/TPBi/LiF/Al	1.12	186	45.9	18.4	This work
ITO/PEDOT: PSS/TFB/CsPbBr3 QDs/TPBi/LiF/Al	75	1,300	2.19	0.87	10
ITO/PEDOT: PSS/PVK/CsCdBr3 Nanorods/TPBi/Liq/Al	600	225	0.5	0.72	56
ITO/P-TPD/CsPbBr3 Nanowire/TPBi/LiF/Al	5.17	3.5	–	–	57
ITO/PEDOT: PSS/ 2D Perovskite/TPBi/Ca/Al	–	12,380	8.4	2.4	58
ITO/PEDOT: PSS/PTAA/CsPbBr3 NPs/TPBi/LiF/Al	35	58,874	–	2.29	59
ITO/PEDOT: PSS/CsPbBr3 QDs/PO-T2 T/Ca/Al	–	14,454	9.22	2.62	60
ITO/PEDOT: PSS/P-TPD/CsPbBr3 /TPBi/LiF/Al	100	24,458	–	9.01	61
ITO/PEDOT: PSS/P-TPD/CsPbBr3 /TPBi/Ag	–	5,711	4.25	1.71	62
FTO/TiO2/MAPbBr3 -NiOx NTs/spiro-OMeTAD/Ag	100	-	5.99	3.9	63
ITO/p-NiO/CsPbBr3 QDs/n-ZnO NPs/Al	–	6,039	7.96	3.79	64
ITO/PEDOT:PSS/P-TPD/PFI/CsPbBr3 /TPBi/LiF/Al	688	1,377	0.19	0.06	65
ITO/PEDOT:PSS/PTAA/CsPbBr3/TPBi/LiF/Al	–	10^4	–	22	66
ITO/PVK/PEDOT:PSS/CsPbBr3/TPBi/LiF/Al	300	5.4 × 10^4	–	22	67
ITO/PEDOT:PSS/PTAA/CsPbBr3/TPBi/LiF/Al	10^3	5000	–	26.7	68
ITO/PEDOT:PSS/HTM/Perovskite QDs/ TPBi/LiF/Al	1000	10^4	–	20.18	69

Figure 6. The logarithm current density vs. voltage curves of single-carrier devices for (a) aspect ratio (AR) of 2.2 and (b) of 2.0 and 1.2, respectively. The insets are schematic illustrations of the hole-only devices.

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