Ligand Engineering for Precise Control of Ultrathin CsPbI3 Nanoplatelet Superlattices for Efficient Light-Emitting Diodes

Jongbeom Kim1,†, Woo Hyeon Jeong2,3,†, Junzhi Ye3,4*, Allison Nicole Arber5, Vikram5, Donghan Kim1, Yi-Teng Huang3,6, Yixin Wang3, Dongeun Kim1, Dongryeol Lee1, Chia-Yu Chang3, Xinyu Shen7, Sung Yong Bae3, Ashish Gaurav3, Ye In Kim1, Jinkyu Yang1, Boseung Je8, Changsoon Cho8, Akshay Rao9, Henry J. Snaith7, M. Saiful Islam5*, Bo Ram Lee2*, Myoung Hoon Song1* Robert L. Z. Hoye3*

1 Department of Materials Science and Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan, 44919 Republic of Korea
2 School of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon, 16419, Republic of Korea
3 Inorganic Chemistry Laboratory, University of Oxford, Oxford, OX1 3QR, United Kingdom
4 Institute of Polymer Optoelectronic Materials and Devices, Guangdong Basic Research Center of Excellence for Energy & Information Polymer Materials, State Key Laboratory of Luminescent Materials and Devices, School of Materials Science and Engineering, South China University of Technology, Guangzhou 510640, China.
5 Department of Materials, University of Oxford, Oxford, OX1 3PH, United Kingdom
6 Graduate Institute of Photonics and Optoelectronics and Department of Electrical Engineering, National Taiwan University, Taipei 10617, Taiwan
7 Clarendon Laboratory, Department of Physics, University of Oxford, Oxford, OX1 3PU United Kingdom
8 Department of Material Science and Engineering, Pohang University of Science and Technology (POSTECH), Pohang, Republic of Korea
9 Cavendish Laboratory, University of Cambridge, Cambridge CB3 0US, United Kingdom



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Figure 1
b: Calculated surface adsorption energy of ligands. Data obtained by Allison Nicole Arber and ViKram
c: Calculated Bader charges of ligands. Data obtained by Allison Nicole Arber and ViKram
d: Liquid-phase 207Pb NMR spectra of PbI2 precursor solutions. Data obtained by Jongbeom Kim
e: in-situ photoluminescence spectra. Data obtained by Jongbeom Kim and Woo Hyeon Jeong
f: Photoluminescence spectra of PeNPL colloidal solutions. Data obtained by Jongbeom Kim
g: Thickness distribution histogram of CsPbI3 PeNPLs determined from TEM. Data obtained by Jongbeom Kim

Figure 2
a-b: Photoluminescence spectra of PeNPL films. Data obtained by Jongbeom Kim and Woo Hyeon Jeong
c: PLQY histogram of PeNPL films. Data obtained by Jongbeom Kim
e: PL intensity histograms extracted from the confocal PL mapping images. Data obtained by Donghan Kim
f-h: Normalized TA spectra from PeNPL films over the first 1000 ps after photoexcitation. Data obtained by Yi-Teng Huang and Yixin Wang

Figure 3
c: X-ray diffraction (XRD) patterns of pristine- and BPAc-PeNPL thin films.  Data obtained by Sung Yong Bae
d: Polarization angle dependence of normalized PL intensity of pristine- and BPAc-PeNPL thin films. Data obtained by Jongbeom Kim and Woo Hyeon Jeong
e-f: Lambertian profile and angular distribution of the normalized PL intensity from PeNPL thin films. Data obtained by Jongbeom Kim

Figure 4
c: Current density–voltage (J–V) curve. Data obtained by Jongbeom Kim
d: Luminance–voltage (L–V) curve. Data obtained by Jongbeom Kim
e: Electroluminescence (EL) spectra. Data obtained by Jongbeom Kim
f: External quantum efficiency (EQE)–current density (EQE–J) curves of champion devices. Data obtained by Jongbeom Kim
g: EQE max histogram from 17 individual PeNPL devices. Data obtained by Jongbeom Kim
h: Comparison of the EQEmax of strongly-confined CsPbX3 (X = I, Br) PeNPL LEDs in the ultrathin regime. Data obtained by Woo Hyeon Jeong

Supplementary Information
Figure S3
a-c: In-situ photoluminescence spectra of PeNPLs in colloidal solution recorded during synthesis. Data obtained by Jongbeom Kim and Woo Hyeon Jeong

Figure S4
In-situ PL spectra during the formation of PeNPLs following the injection of the Cs-oleate into the PbI2 solution. Data obtained by Jongbeom Kim and Woo Hyeon Jeong

Figure S5
Time-resolved evolution of the PL peak wavelength during growth. Data obtained by Jongbeom Kim and Woo Hyeon Jeong

Figure S6
In-situ PL intensity changes of during synthesis of PeNPLs with different ancillary ligands. Data obtained by Jongbeom Kim and Woo Hyeon Jeong

Figure S7
Ultraviolet-visible absorption (dashed lines) and photoluminescence (solid lines) spectra of PeNPLs films. Data obtained by Jongbeom Kim.

Figure S10
a Size distribution and b aspect ratio histogram of each PeNPLs determined from TEM measurements from Figure S8 Data obtained by Jongbeom Kim and Chia-Yu Chang

Figure S11
1H-NMR results of pristine-, BPAc- and DPPAc-PeNPLs. Data obtained by Jongbeom Kim.

Figure S12
PLQY distributions of PeNPL colloidal solutions. Data obtained by Jongbeom Kim.

Figure S10
XPS spectra of each PeNPLs. Data obtained by Woo Hyeon Jeong and Jongbeom Kim.

Figure S11
1H-NMR spectra of each PeNPLs before and after aging. Data obtained by Woo Hyeon Jeong and Jongbeom Kim.

Figure S12
PLQY distributions of collidal PeNPLs. Samples were measured by Quantaurus-QY Absolute PL quantum yield spectrometer (HAMAMATSU). Data obtained by Jongbeom Kim.

Figure S13
Excitation fluence-dependent time-resolved photoluminescence decay curves of PeNPL films. Data obtained by Junzhi Ye

Figure S14 
Transient absorption spectroscopy measurements of PeNPL solutions. Data obtained by Yi-Teng Huang and Yixin Wang

Figure S15
b-c: 1H-NMR spectra of colloidal PeNPLs dispersed in deuterated DMSO. Data obtained by Jongbeom Kim

Figure S16
a: 207Pb NMR spectra of PeNPLs dissolution in deuterated DMSO. Data obtained by Jongbeom Kim
b: 31P NMR spectra of PeNPLs dissolution in deuterated DMSO. Data obtained by Jongbeom Kim

Figure S17
XPS spectra of PeNPL films. Data obtained by Jinkyu Yang

Figure S18
Fourier-transform infrared spectroscopy spectra of PeNPLs powder. Data obtained by Ye In Kim

Figure S19
PL spectra of PeNPL thin films. Data obtained by Jongbeom Kim

Figure S20
PLQY distributions of PeNPL thin films. Data obtained by Jongbeom Kim

Figure S21-22
Grazing-incidence wide-angle X-ray scattering (GIWAXS) patterns of edge-up oriented PeNPL thin films. Data obtained by Jongbeom Kim

Figure S23-4
One-dimensional GIWAXS profiles integrated over all azimuthal angles in the low-angle regions for PeNPL films.  Data obtained by Jongbeom Kim

Figure S25-6
Azimuthal angle (χ) dependence of (100) diffraction peak intensity for PeNPL thin films. Data obtained by Jongbeom Kim

Figure S27-28
in X-ray diffraction (XRD) patterns of edge-up oriented each PeNPL thin films. Data obtained by Sung Yong Bae and Jongbeom Kim

Figure S30
Polarization dependence of the normalized PL intensity of each PeNPLs thin films made in different batches. Data obtained by Jongbeom Kim and Woo Hyeon Jeong

Figure S31
Histogram showing the distribution in the degrees of polarization displayed in Figure S30. Data obtained by Jongbeom Kim and Woo Hyeon Jeong

Figure S32
Optical simulation of the relative external quantum efficiency of PeNPLs LED device as a function of vertical dipole ratio. Data obtained by Boseung Je and Changsoon Cho

Figure S33
Refractive index of PeNPLs film as a function of wavelength. Data obtained by Boseung Je and Changsoon Cho

Figure S34
BPAc-PeNPL LED devices based on PeNPLs that have an overall edge-up orientation. Data obtained by Jongbeom Kim

Figure S35
Normalized EL spectra of Pristine- and BPAc-PeLEDs under varying applied voltages. Data obtained by Jongbeom Kim

Figure S36
Device stability test from half lifetime measurements (T50) of Pristine- and BPAc-PeLED devices measured under ambient conditions with encapsulation. Data obtained by Jongbeom Kim

Figure S37
Comparison of the EQEmax of CsPbI3 perovskite nanocrystal-based LED devices. Data obtained by Woo Hyeon Jeong





