Supporting Information

Cesium Copper Iodide Tailored Nanoplates and

Nanorods for Blue, Yellow and White Emission

Parth Vashishtha,†* Gautam V. Nutan,† Benjamin E. Griffith,∥ Yanan Fang,† David

Giovanni,§ Metikoti Jagadeeswararao,‡ Tze Chien Sum,§ Nripan Mathews,†‡ Subodh G.

Mhaisalkar,†‡ John V. Hanna,∥†* Tim White†*

†School of Materials Science and Engineering, Nanyang Technological University (NTU), 50

Nanyang Avenue, Singapore 639798, Republic of Singapore

‡Energy Research Institute @NTU (ERI@N), Research Techno Plaza, X-Frontier Block,

Level 5, 50 Nanyang Drive, Singapore 637553, Republic of Singapore

∥Department of Physics, University of Warwick, Coventry CV4 7AL, United Kingdom

§Division of Physics and Applied Physics, School of Physical and Mathematical Sciences,

Nanyang Technological University, 21 Nanyang Link, Singapore, 637371, Republic of

Singapore

Figure S1. XPS spectra of (a) Cs 3d scan shows the +1 oxidation state , (b) Cu 2p scan

shows the +1 oxidation state of Cu in both samples coupled with I 3p peak & Cs MNN auger

peak. To eliminate the Cs MNN auger peak and identify the coupling of I 3p peak, Cu 2p

scan was re-performed with different x-ray source (Ag) with wide range scan (970-865 eV),

(c) I 3d scan shows the -1 oxidation state of iodine in Cs3Cu2I5 NPs and CsCu2I3 NRs.

Overall, XPS data supports the corresponding oxidation state of each element in Cs3Cu2I5 and

CsCu2I3.

Figure S2. Absorption spectra of Cs3Cu2I5 NPs and CsCu2I3 NRs with sharp absorption edge

at 285 and 321, respectively.

Figure S3. Emission spectra of (a) Cs3Cu2I5 NPs and (b) CsCu2I3 NRs at different excitation

wavelength ranges from 290 nm to 340 nm. No notable peak shift or secondary peak were

found by varying the excitation wavelength.

Figure S4. XRD spectra of (a) Cs3Cu2I5 NPs and (b) CsCu2I3 NRs after keeping the samples

for 2 months in ambient condition. No significant difference in the crystal structure

demonstrates the stability of this material for optoelectronic applications.

Figure S5. (a) XRD and (b) PLE and PL spectra of Cs3Cu2I5 NPs and CsCu2I3 NRs synthesized

using 2-HAD as an organic ligand instead of oleic acid. No significant improvement in optical

and structural properties were found. Moreover, the solubility of NRs became even poorer

while using 2-HDA.

Figure S6. Schematic representation of self-trapped exciton mechanism in Cs3Cu2I5 NPs and

CsCu2I3 NRs as a results of the Jahn-Teller distortion or exciton-phonon coupling.1-2

Figure S7. TEM Micrographs of Cs3Cu2I5 synthesised at 70 °C using hot-injection method.

NPs appeared to be larger in size and most likely agglomerated. NPs surface was also found to

be relatively rough and uneven.

Figure S8. Scanning Electron Microscopy (SEM) micrographs of (a) Cs3Cu2I5 NPs and (b)

CsCu2I3 NRs.

Figure S9. A histogram for CsCu2I3 NRs length. The average length of NRs is ~201 nm,

which gives the aspect ratio of 1:3.

Table S1: EDXS data of Cs3Cu2I5 NPs drop casted on ITO substrate. Elemental analysis

confirms the estimated ratio of 2.94:2.00:5.62 between Cs:Cu:I.

Table S2: EDXS data of CsCu2I3 drop casted on ITO substrate. Elemental analysis confirms

the estimated ratio of 1.02:2.00:3.50 between Cs:Cu:I.

Table S3. Refined position coordinates for Cs3Cu2I5 NPs

Atom Wyck. Occupancy x/a y/b z/c

Cs1 4c 1 0.5948(5) 1/4 0.5506(4)

Cs2 8d 1 0.0524(4) 0.9897(4) 0.6783(2)

Cu1 4c 1 0.2409(1) 1/4 0.3701(8)

Cu2 4c 1 0.2125(9) 1/4 0.5473(7)

I1 8d 1 0.6918(3) 0.5609(3) 0.5516(3)

I2 4c 1 0.1574(5) 1/4 0.2069(4)

I3 4c 1 0.9682(5) 1/4 0.5108(4)

I4 4c 1 0.3012(6) 1/4 0.7163(4)

Table S4. Refined position coordinates for CsCu2I3 NRs

Atom Wyck. Occupancy x/a y/b z/c

Cs1 4c 1 0 0.6722(2) 1/4

Cu1 8e 1 0.8510(1) 0 0

I1 4c 1 0 0.1204(2) 1/4

I2 8g 1 0.7170(1) 0.8810(2) 1/4

No. Cs Cu I

1 28.14 17.41 54.46

2 27.35 20.10 52.56

3 25.90 17.84 56.26

4 27.60 19.02 53.38

5 29.81 20.10 49.03

Mean ± Std. deviation 27.76 ± 1.26 18.89 ± 1.11 53.13 ± 2.39

Ratio 2.94 2 5.62

No. Cs Cu I

1 15.28 30.55 54.17

2 16.98 30.27 52.75

3 14.82 32.79 52.40

4 15.40 31.77 52.83

5 15.61 26.73 57.66

6 15.47 32.07 52.46

Mean ± Std. deviation 15.59 ± 0.66 30.7 ± 1.97 53.712 ± 1.86

Ratio 1.02 2 3.5

Table S5. Elemental composition of Cs3Cu2I5 NPs and CsCu2I3 NRs measured by XPS

(Figure S1).

Element Cs3Cu2I5 NPs CsCu2I3 NRs

Cs 2.90 0.92

Cu 2.05 2.04

I 5.15 2.91

References:

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Efficient and stable emission of warm-white light from lead-free halide double perovskites.

Nature 2018, 563 (7732), 541.

2. Roccanova, R.; Yangui, A.; Nhalil, H.; Shi, H.; Du, M.-H.; Saparov, B., Near-Unity

Photoluminescence Quantum Yield in Blue-Emitting Cs3Cu2Br5–xIx (0≤ x≤ 5). ACS Applied

Electronic Materials 2019, 1(3), 269-274.