Taming quantum dots’ nucleation and growth enables stable and efficient blue-light-emitting devices

Zhiwei Ma; Junxia Hu; Liping Tang; Bingbing Lyu

doi:10.1364/PRJ.462852

Journals >Photonics Research >Volume 10 >Issue 10 >Page 2359 > Article

Photonics Research
Vol. 10, Issue 10, 2359 (2022)

Taming quantum dots’ nucleation and growth enables stable and efficient blue-light-emitting devices

Zhiwei Ma^1、2、*, Junxia Hu³, Liping Tang³, and Bingbing Lyu⁴

Author Affiliations

¹Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing 100049, China

²Key Laboratory for Special Functional Materials of the Ministry of Education, Henan University, Kaifeng 475004, China

³School of Information Engineering, Xinyang Agriculture and Forestry University, Xinyang 464000, China

⁴Department of Physics, South University of Science and Technology, Shenzhen 518055, China

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DOI: 10.1364/PRJ.462852 Cite this Article Set citation alerts

Zhiwei Ma, Junxia Hu, Liping Tang, Bingbing Lyu. Taming quantum dots’ nucleation and growth enables stable and efficient blue-light-emitting devices[J]. Photonics Research, 2022, 10(10): 2359 Copy Citation Text

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(a) Schematic diagram of the preparation process of ZnxCd1−xSeyS1−y cores and gradient ZnCdSeS/ZnS alloy QDs with different emissions and nanostructures. (b) ZnCdSeS/ZnS alloy QDs with the evolution of spectra from violet to yellow. Inset: PL images of ZnCdSeS/ZnS alloy QDs with different emission colors. (c) Full width at half maximum (FWHM) and (d) PL QY of ZnCdSeS/ZnS alloy QDs with the given peak. (e) Zn/Cd and S/Se composition ratio of ZnxCd1−xSeyS1−y cores based on ICP-OES data.

Fig. 1. (a) Schematic diagram of the preparation process of ZnxCd1−xSeyS1−y cores and gradient ZnCdSeS/ZnS alloy QDs with different emissions and nanostructures. (b) ZnCdSeS/ZnS alloy QDs with the evolution of spectra from violet to yellow. Inset: PL images of ZnCdSeS/ZnS alloy QDs with different emission colors. (c) Full width at half maximum (FWHM) and (d) PL QY of ZnCdSeS/ZnS alloy QDs with the given peak. (e) Zn/Cd and S/Se composition ratio of ZnxCd1−xSeyS1−y cores based on ICP-OES data.

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Time-dependent PL spectra of (a) blue-violet, (b) blue, and (c) sky-blue ZnCdSeS/ZnS alloy QDs. Inset: schematic of QDs’ energy alignments and exciton delocalization. (d) Time-resolved PL decay kinetics, (e) temperature-dependent PL peak, and (f) intensity of blue-violet, blue, and sky-blue ZnCdSeS/ZnS alloy QDs.

Fig. 2. Time-dependent PL spectra of (a) blue-violet, (b) blue, and (c) sky-blue ZnCdSeS/ZnS alloy QDs. Inset: schematic of QDs’ energy alignments and exciton delocalization. (d) Time-resolved PL decay kinetics, (e) temperature-dependent PL peak, and (f) intensity of blue-violet, blue, and sky-blue ZnCdSeS/ZnS alloy QDs.

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Fig. 3. (a) Schematic illustrating the structure and (b) energy level diagram of QLEDs. (c) Ultraviolet photoelectron spectroscopy of blue-violet, blue, and sky-blue QDs. (d) Current–voltage measurements for hole-only devices, where the devices were formed from sky-blue, blue, and blue-violet QDs. (e) Current density luminance versus driving voltage characteristics and (f) EQE as a function of luminance of the performing QLEDs based on blue-violet, blue, and sky-blue QDs.

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Fig. 4. AFM measurements show the root mean square (RMS) roughness for the following layers: (a) PEDOT:PSS, (b) TFB, and (c) ZnO. RMS of (d) sky-blue, (e) blue, and (f) blue-violet ZnCdSeS/ZnS alloy QDs.

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Fig. 5. (a) EL spectra and photographs of QLEDs, and (b) corresponding CIE coordinates of the three QLEDs. (c) Luminance versus time of operation under ambient conditions of blue-violet, blue, and sky-blue QLEDs.

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Fig. 6. (a)–(e) TEM images of ZnxCd1−xSeyS1−y cores with emission spectra from violet to yellow, respectively. Inset shows the size distribution of the ZnxCd1−xSeyS1−y cores.

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Fig. 7. (a)–(e) TEM images of ZnCdSeS/ZnS with emission spectra from violet to yellow, respectively. Inset shows the size distribution of QDs. Scale bar: 20 nm.

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$X-ray powder diffraction pattern of zinc-blende ZnCdSeS/ZnS QDs with emission spectra from violet to yellow.$

Fig. 8. X-ray powder diffraction pattern of zinc-blende ZnCdSeS/ZnS QDs with emission spectra from violet to yellow.

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Fig. 9. TEM Images of (a) blue-violet, (b) blue, and (c) sky-blue ZnCdSeS/ZnS alloy QDs. Inset shows the size distribution of ZnCdSeS/ZnS alloy QDs.

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TOP (mmol)	Zn	Cd	Se	S	QD Core Composition
3.00	0.69	0.31	0.08	0.92	${Zn}_{0.69} {Cd}_{0.31} {Se}_{0.08} S_{0.92}$
3.43	0.62	0.38	0.09	0.91	${Zn}_{0.62} {Cd}_{0.38} {Se}_{0.09} S_{0.91}$
3.64	0.56	0.44	0.15	0.85	${Zn}_{0.56} {Cd}_{0.44} {Se}_{0.15} S_{0.85}$
3.86	0.35	0.66	0.19	0.81	${Zn}_{0.35} {Cd}_{0.65} {Se}_{0.19} S_{0.81}$
4.29	0.29	0.71	0.24	0.76	${Zn}_{0.29} {Cd}_{0.71} {Se}_{0.24} S_{0.76}$
5.36	0.2	0.71	0.28	0.72	${Zn}_{0.29} {Cd}_{0.71} {Se}_{0.28} S_{0.72}$
6.43	0.24	0.76	0.32	0.68	${Zn}_{0.24} {Cd}_{0.76} {Se}_{0.32} S_{0.68}$

Table 1. Zn_xCd_1−xSe_yS_1−y Cores with a Chemical Composition

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Color	$τ_{1}$ (ns)	$τ_{2}$ (ns)	$f_{1}$ (%)	$f_{2}$ (%)	$T$ (ns)	$χ_{R}^{2}$
Sky-blue	8.74	19.63	27.54	72.46	16.6	1.11
Blue	6.23	17.73	19.31	80.69	15.5	1.23
Blue-violet	6.46	18.72	23.47	76.53	15.8	1.25

Table 2. Lifetimes and Fractional Contribution of Different PL Decay Channels for Sky-Blue, Blue, and Blue-Violet ZnCdSeS/ZnS Alloy QDs in Solution^a

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QDs	EL (nm)	$L_{\max}$ ( $cd / m^{2}$ )	Peak EQE (%)	Lifetime ( $h$ ) at $100 cd / m^{2}$	Reference
ZnCdS/ZnS	455	4000	10.7	$< 1000$	[9]
	468	4890	19.8	47.4	[14]
${Zn}_{x} {Cd}_{1 - x} S / ZnS$	445	4500	15.6	47 ( $420 cd / m^{2}$ )	[39]
ZnCdSe/ZnS/ZnS	479	14,100	16.2	355	[40]
ZnCdSe/ZnSe	482	62,600	8.05	7000	[10]
CdZnS/ZnS	454	27,753	8.92	–	[18]
CdSeS/ZnSeS/ZnS	483	/	$\sim 10$	10,000	[41]
ZnCdSeS/ZnS	443	6442	10.0	3813	This work
	462	14,390	15.8	10,420
	472	21,130	13.4	11,287

Table 3. Summary of EL Performance, Maximum Luminance (Lmax), EQE, and Lifetime of Optimized Best Performing QLEDs

Zhiwei Ma, Junxia Hu, Liping Tang, Bingbing Lyu. Taming quantum dots’ nucleation and growth enables stable and efficient blue-light-emitting devices[J]. Photonics Research, 2022, 10(10): 2359

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