Emission Properties and Ultrafast Carrier Dynamics

of CsPbCl3 Perovskite Nanocrystals

Ruben Ahumada-Lazo1, Juan A. Alanis1, Patrick Parkinson1, David J. Binks1*, Samantha. J. O.

Hardman2, James T. Griffiths3, Florencia Wisnivesky Rocca Rivarola3, Colin J. Humphrey3, ‡,

Caterina Ducati3, Nathaniel. J. L. K. Davis4, †

1School of Physics and Astronomy and the Photon Science Institute, University of Manchester,

Manchester, M13 9PL, United Kingdom

2Manchester Institute of Biotechnology, University of Manchester, Manchester, M13 9PL,

United Kingdom

3Department of Materials Science and Metallurgy, University of Cambridge, Charles Babbage

Road, Cambridge, CB3 0FS, United Kingdom

4 Cavendish Laboratory, University of Cambridge, J. J. Thompson Avenue, Cambridge, CB3

0HE, United Kingdom

Author’s current affiliations:‡School of Engineering and Materials Science, Queen Mary University of London, London, E1 4NS, United Kingdom.†School of Chemical and Physical Sciences, Victoria University of Wellington, Wellington 6140, New Zealand

1

ABSTRACT

Fluence-dependent photoluminescence and ultrafast transient absorption spectroscopy are used

to study the dynamic behavior of carriers in CsPbCl3 perovskite nanocrystals. At low excitation

fluences, the radiative recombination rate is outcompeted by significant trapping of the charge

carriers which then recombine non-radiatively, resulting in weak photoluminescence. As fluence

is increased, the saturation of trap states deactivates these non-radiative relaxation paths giving

rise to an increase in photoluminescence at first. However, with further increases in fluence,

Auger recombination of multiexcitons results in a decline in photoluminescence efficiency.

Analysis of this behavior yields an absorption cross-section at 400 nm (3.1 eV) of 0.24 ± 0.05 x

10-14 cm2. Transient photoluminescence and absorption measurements yielded values for single

exciton trapping lifetime (1.6 ± 0.7 ns), biexciton and trion lifetimes (20 ± 3 ps and 157 ± 20 ps,

respectively), single exciton radiative lifetime (12.7 ± 0.2 ns), intraband cooling lifetime (290 ±

37 fs) and exciton-exciton interaction energy (10 ± 2 meV).

2

INTRODUCTION

Ionic metal-halide perovskite nanocrystals (NCs), with the general formula ABX3, where A is a

large cation, B a metal (Pb, Sn being the most studied), and X a halide (Cl, Br, I), have received

significant attention because their optical properties make them suitable for many optoelectronic

applications. 1 In particular, all-inorganic CsPbX3 NCs exhibit bright and tunable emission and

have recently emerged as promising candidates to replace chalcogenide-based quantum dots

(QDs), which are more susceptible to photodegradation. 2 The spectral properties of this type of

NCs can be tuned by size (making use of the quantum confinement effect) or by halide

composition, with emissions shifting from blue (Cl-), to green (Br-), to red (I-) in NCs of the same

size. Moreover, halide exchange (of similar size anions, i.e. Cl- and Br- or Br- and I-) allows for

mixed compositions with emission covering the entire visible spectrum. 3 In contrast, when NCs

of CsPbI3 and CsPbCl3 are mixed together, the anion exchange is significantly reduced due to the

unfavorable crystal lattice tolerance factor for iodide−chloride exchange, allowing for excitation

transfer from CsPbCl3 to CsPbI3 via radiative emission. 4 CsPbX3 materials are easily synthesized

by a low-cost solution method which produces monodispersed NCs that are more stable than

hybrid organic-inorganic perovskites. 5 They are also highly ionic and stoichiometric which

reduces the number of structural defects that can act as carrier traps, giving high

photoluminescence (PL) quantum yields (PLQYs) without the need of core/shell structures.2

However, the high surface-to-volume ratio of NCs can inherently induce significant trapping of

carriers at the dangling bonds of undercoordinated surface atoms if these are not properly

passivated. 6 Moreover, because of the ionic nature of these all inorganic perovskites, their

interactions with capping ligands are also very ionic and unstable, making their colloidal

solubility, PLQY and even their structural integrity highly susceptible to reaction conditions and

3

purification methods. 7 In addition, photochemical degradation has been observed to decrease the

PL emission intensity in perovskite NCs exposed to laser light by creating surface defects which

act as non-radiative recombination centers. 8

These newly developed materials are very promising for applications as varied as quantum

emitters, 8 color-converting phosphors, 9 lasers, 10 photovoltaics 11 and light-emitting diodes. 12,13

This has motivated the study of the carrier dynamics and quantum confinement effects for

different sizes and compositions of this family of perovskites. 14 A few studies have reported the

dynamics of single and multi-excitons in CsPbI3, CsPbBr3 and mixed CsPbI1.5Br1.5 compositions,

finding very interesting similarities and differences with more common colloidal QDs 14–16. For

example, in perovskite NCs the decay of multiexcitons and charged excitons is also dominated

by very fast Auger recombination. Biexciton lifetimes have been found to scale linearly with NC

volume, V, regardless of the differences in electronic structure for many of the different types of

quantum dots studied in the literature. Perovskite NCs also follow this trend but only when under

the strong confinement regime, i.e. NCs with edge lengths close to or less than the exciton Bohr

radius. Larger perovskite NCs (in the weak confinement regime) deviate from this “universal

volume scaling” showing lifetimes with sublinear dependencies on V. 14,16 In addition, the

absorption cross-sections of these NCs have been found to also scale linearly with volume as in

other QDs, but are almost an order of magnitude smaller than those of CdSe QDs of the same

size. 14 The sub-picosecond intraband relaxation of hot carriers in perovskite quantum dots is also

of interest because its exact mechanism is still not fully understood. This is believed to happen

through either Auger energy transfer, coupling to surface ligands or multiphonon emission in

quantum dots, in contrast to the phonon emission cascade observed for bulk materials. 14

4

Understanding these properties is fundamental for the further development of devices based on

perovskite NCs. However, studies on carrier dynamics have not yet been extended to CsPbCl3,

which is of interest because of its bright and spectrally-narrow blue luminescence. 2 In the

present work we use fluence-dependent photoluminescence (PL) and ultrafast transient

absorption (TA) techniques to uncover the dynamic behavior of carriers under different

excitation regimes in CsPbCl3 NCs.

EXPERIMENTAL METHODS

Nanocrystal synthesis

NCs CsPbCl3 were prepared using a solution based method previously reported by Protesescu

et al. 2 and deposited on transparent support films for PL and CL measurements. Briefly: Cs2CO3

(0.814 g, 99.9%) was loaded into 100 mL three-neck flask along with octadecene (ODE, 30 mL,

90%) and oleic acid (2.5 mL, OA, 90%), the mixture was dried for 2 h at 120 °C under N 2. The

solution temperature was then lowered to 100 °C. ODE (75 mL), oleylamine (7.5 mL, OLA,

90%), and dried OA (7.5 mL, PbCl2 (0.675g, 99.99%) and 5 mL of trioctylphosphine (TOP,

97%) (to solubilize PbCl2) were loaded into a 250 mL three-neck flask and dried under vacuum

for 2 h at 120 °C. After complete solubilization of the PbCl2 salt, the temperature was raised to

170°C and the Cs-oleate solution (6.0 mL, 0.125 M in ODE, prepared as described above) was

quickly injected. After 10 s, the reaction mixture was cooled in an ice-water bath. The NCs were

transferred to an argon purged glove box (H2O and O2 < 1 ppm) precipitated from solution by the

addition of equal volume anhydrous butanol (BuOH, 99%) (ODE:BuOH = 1:1 by volume). After

centrifugation, the supernatant was discarded and the NCs were redispersed in anhydrous hexane

(99%) and precipitated again with the addition of BuOH (hexane:BuOH = 1:1 by volume). These

5

were redispersed in hexane. The nanocrystal dispersion was filtered through a 0.2 μm PTFE filter

and diluted in hexane before use. Sample concentrations were determined by allowing the

solvent from a known volume to evaporate and then weighing the residue. Details of the sample

preparation for TA are given in the supporting information.

Scanning transmission electron microscopy and Nano-cathodoluminescence

Samples for STEM were prepared by drop-casting 40 mg/mL perovskite nanocrystal solution

in hexane on a carbon coated 200 mesh copper grid in an argon filled glove box. Atomic

resolution ADF-STEM was performed on a probe corrected FEI Titan, at 300 keV with 60 pA.

Nano-CL was performed in a STEM operated at 80 kV. Miniature elliptical mirrors positioned

around the specimen were used to collect the light emitted from each position in the sample as

the sub-nanometre electron probe was rastered across the specimen. The collected light was

coupled to optical fibers and detected on a photomultiplier tube.

Photoluminescence (PL) measurements

The steady state PL was measured using a FluoroLog 3 spectrometer.

Ensembles of the NCs were studied by fluence-dependent photoluminescence (PL)

spectroscopy. This was performed using a pulsed Ti:sapphire (RegA 9000) laser source at a

repetition rate of 250 kHz and 170 fs pulse duration. A frequency doubler (PHOTOP TP-2000B)

was used to generate the excitation wavelength of 400 nm. The laser fluence was varied with a

neutral density filter wheel and measured by a power meter. The spot size at the sample position

was measured to be 1.3 x 10-3 mm2 after defocusing with an objective lens. The emitted light was

collected by an optic fiber and directed into a spectrometer (Ocean Optics) after passing through

6

a long pass filter to eliminate scattered light from the source. More details of this experimental

setup are given in reference 17.17

Photoluminescence decay transients were recorded using a time correlated single photon

counting (TCSPC) system previously reported. 18 Here, a mode-locked Ti:sapphire laser (Mai-

Tai HP, Spectra Physics) is used to produce 100 fs pulses at a repetition rate of 80 MHz and 720

nm wavelength. The repetition rate is then reduced to 4 MHz by an acousto-optic pulse picker

(APE Select) and the initial wavelength halved (to 360 or 400 nm) via second harmonic

generation (APE harmonic generator). These pulses were passed through a lens with 5 cm focal

length to reduce the spot size and a series of neutral density filters were used to excite the

solution of NCs with an range of photon fluences from ~1.7 x 10-13 to ~4 x 10-14 photons·cm-2 per

pulse. The PL emission of the samples was collected and focused after a 405 nm pass-band filter

into a monochromator (Spex 1870c) and detected at the PL peak by a multi-channel plate

(Hamamatsu R3809U-50). The time correlation of the detected photons was performed using a

PC electronics card (TCC900) from Edinburgh Instruments.

Absorption and Transient absorption (TA) measurements

Steady-state absorption spectra were taken using a Perkin Elmer lamda-1050 spectrometer.

A previously reported 19 Ti:sapphire amplifier system (Spectra Physics Solstice Ace) was used

to generate 800 nm pulses at 1 kHz for the TA experiments. A portion of this beam was used to

pump an optical parametric amplifier (Topas Prime) with an associated NIR-UV-Vis unit to

achieve the 100 fs pump pulses at 350 nm with a beam diameter of 360 μm. The pulse energy

could be reduced using a series of reflective neutral density filters to give pump fluences from ~3

x 1012 to ~3 x 1015 photons·cm2 per pulse. The rest of the laser output was passed through a CaF2

7

crystal to generate a white light continuum which was used as the probe to record changes in

absorption between 360 and 750 nm. Ultrafast broadband transient absorption measurements

were carried out at randomly ordered time points in a Helios (Ultrafast Systems LLC)

spectrometer (-5 ps to 3 ns, ∼0.2 ps resolution). The sample was magnetically stirred to avoid

photocharging effects during the measurements.

RESULTS AND DISCUSSION

The sample analyzed in this study consisted of irregular CsPbCl3 NCs with a range of sizes and

aspect ratios as can be seen in the scanning transmission electron microscope (STEM) image

inset in figure 1. The average length of the nanocrystals in the sample is 8 nm and standard

deviation of the length distribution was ± 2 nm. Since the exciton Bohr radius for CsPbCl3 is

2.5 nm, these nanocrystal sizes correspond to the weak confinement regime and so little or no

size-dependence to their properties is expected2. The size dispersion is approaching that

typically demonstrated for similarly-sized CsPbBr3 nanocrystals, with values of 8.1 ± 1.1 nm and

7.7 ± 1.1 nm reported.14,15 Further details about size distribution of the sample and the size and

shape dependence of emission are given in the Supporting Information. The lattice of the atomic

structure (figure 1 inset) corresponds to the thermally-stable cubic perovskite crystal structure,

with no extended defects; we therefore attribute the trapping processes described below to

surface states. Also shown in figure 1 are the steady-state absorbance and PL spectra. The

absorbance spectrum (continuous line) shows a steep onset and a very clear feature at 3.08 eV

(403 nm) which is identified with the first excitonic state. Absorption peaks corresponding to a

second and third excited state can also be seen at 3.18 eV (390 nm) and 3.30 eV (375 nm),

respectively. The photoluminescence spectrum (dashed line) shows an emission peak centered at

8

3.05 eV (406 nm) with a 80 meV linewidth at the FWHM, which is comparable to that of

previously reported perovskite NCs. 2 The inset also shows a photograph of the bright blue

emission observed from a solution of CsPbCl3 NCs with a concentration of 1 mg/mL under UV

excitation (365 nm).

Figure 1. Absorption and PL spectra of a solution of CsPbCl3 NCs. Inset shows high resolution

STEM images and a photograph of the blue emission under UV radiation.

In figure 2, the relative photoluminescence quantum efficiency,QEPL(defined as the ratio

between the time-averaged, spectrally-integrated PL signal and the excitation fluence,

normalized to the maximum value of this ratio) is plotted as a function of the photon fluence of

the excitation laser pulse,J p. The sample consisted of a film of CsPbCl3 NCs (0.1 ml of a 20

9

mg·ml-1) deposited on a quartz substrate (0.8 cm2). As can be seen, the QEPL first increases with

photon fluence then remains approximately constant for moderate fluences before finally

reducing as the photon fluence is further increased. This behavior can be explained by

considering how the competition between trapping, radiative recombination and Auger

recombination changes with photon fluence. (Shallow surface traps have been reported to arise

from lead-rich surfaces, i.e. uncoordinated Pb atoms due to surface Pb - Cl ion pair vacancies in

this type of NCs, affecting the PLQYs and giving multiexponential PL decays.20,21) For low

fluences, there is negligible probability that one NC will absorb more than one photon per

excitation pulse, so only single excitons are produced. The photoluminescence efficiency thus

depends on both the fraction of NCs that are trap-free, and hence completely emissive, and the

competition between radiative recombination and non-radiative trap-mediated recombination

pathways in those NCs with traps. The increasing saturation of traps produced as the excitation

fluence is increased results in the growth of QEPL observed initially. As only single excitons are

created in a NC at low fluences, this saturation corresponds to the deactivation of a non-radiative

recombination channel for longer than the interval between excitation pulses (4 μs in this study).

Long-lived changes in the emission properties of perovskite NCs of up to 1 s in duration have

been observed in PL intermittency studies. 8

With further increase in fluence, the probability of more than one photon being absorbed per

nanocrystal per pulse is now no longer negligible. This results in the increase in QEPL due to trap

saturation being offset by a decrease in QEPL due to Auger recombination of multiple excitons.

Initially, these two effects broadly balance each other giving rise to a plateau region over a small

fluence range (~4 - 9 x 1013 photons.cm-2). Since Auger recombination has a characteristic

lifetime that is much shorter than that of radiative recombination 14 and thus dominates when

10

multi-excitons form, theQEPLcontinues to reduce with further increase in fluence as the

formation of multiexcitons becomes more and more prevalent.

To understand this trend with relation to the number of excitons in each NC, the absorption

cross-section, σ , was found by fitting the data in figure 2 to the following equation:

QEPL=S ( ⟨ N ⟩ )+ ⟨ N ⟩e−⟨ N ⟩

1−e−⟨ N ⟩ (1).

where ⟨ N ⟩=σ J p is the average number of photons absorbed per nanocrystal per excitation

pulse. Equation (1) was derived by combining a sigmoidal growth function 22,, S ( ⟨ N ⟩ ), with an

expression based on the assumption that photon absorption events follow a Poisson distribution

and single excitons are significantly more likely to recombine radiatively and contribute to the

PL than multiexcitons 14. The derivation of this equation is detailed in the supporting

information. This cross-section was found to be σ = (0.24 ± 0.05) x 10-14 cm2 for an excitation

photon energy of 3.1 eV (400 nm), which is in good agreement with values reported for CsPbI3

and CsPbBr3 when scaled to match the NC sizes using the linear dependency with volume

observed previously. 14 This σ value was used to calculate the values of ⟨ N ⟩ plotted along the top

horizontal axis in figure 2. Similar data obtained from a solution of the NCs is shown in the

Supporting Information.

11

Figure 2. Normalized photoluminescence quantum efficiency, QEPL , as function of photon

fluence,J p, and average number of photons absorbed per pulse per nanocrystal, ⟨ N ⟩. The fit

shown is to eqn. S1.1

Figure 3a-c show contour plots of the pump-induced absorption change, ∆ A, spectra as a

function of delay time for NC samples in solution at three representative pump fluences

corresponding to ⟨ N ⟩ = 0.007, 0.11 and 6.73 (as calculated from the excitation fluence using the

absorption cross-section obtained from the fitting to the QEPL data as described above). A strong

bleach feature (negative ∆A shown in green and blue) centered at 403 nm is observed in all the

plots. This feature corresponds to the lowest-energy absorption feature identified in the steady-

state absorption spectrum and is attributed to state-filling of the 2-fold degenerate band-edge

states, as previously reported. 14 Photoinduced absorption features (positive ∆A shown in red) are

12

also observed at both sides of the bleach peak. All these features progressively become more

intense and broad as the pump fluence and hence ⟨ N ⟩ are increased. Similar plots for the other

pump fluences used in this study are shown in the Supporting Information.

Figure 3d shows fractional absorption change, ∆A/A, transients recorded at the 403 nm bleach

peak for different ⟨ N ⟩ values. For low pump fluences where ⟨ N ⟩ << 1, excited NCs only

contain a single exciton and the resulting transients are well described by a mono-exponential

decay function with a characteristic time constant,τ1 T , of 1.6 ± 0.7 ns which corresponds to the

lifetime of single band-edge excitons; this large relative error is a consequence of restricting the

monoexponential fit to the low fluence transients, which have the lowest signal-to-noise ratio.

The radiative lifetime of CsPbCl3 NCs has not been reported but since this decay component is

observed for values of ⟨ N ⟩ = 0.007 when QEPL is significantly less than unity, it is attributed to

trapping. This is further confirmed by the fits to the PL decays shown in figure S5 in the

supporting information for a range of excitation fluences.

13

Figure 3. a-c) Contour plots of the change in absorption, ∆A , as a function of wavelength and

delay time recorded at different ⟨N⟩. d) ∆A/A transients for all ⟨N⟩ at the wavelength

corresponding to the absorption bleach peak (403 nm). Continuous lines are exponential fits to

the data decay, starting from the maximum amplitude of the peaks.

As ⟨ N ⟩ increases with fluence, an additional and more rapid decay component begins to

develop and grows in amplitude, with the decay of the transients now better described by a bi-

exponential function. This fluence-dependent decay component is attributed to the Auger

recombination of biexcitons 14 and the associated lifetime, τ 2 A, was determined by a global

biexponential fit to the decay transients, where one of the constants was fixed to the value

14

obtained from the low fluence transient. This process yielded a τ 2 A value of 20 ± 3 ps. The

lifetime for the Auger recombination of biexcitons in CsPbI3 NCs has been reported to be 92 ±

1 ps 14, whereas reports for CsPbBr3 14,15 range from 25 ps to 50 ps depending on the nanocrystal

volume.

For pump fluences such that⟨ N ⟩≥1, the decay transients are no longer well described by a

biexponential, requiring a third decay component with an associated lifetime, τ 2 A∗¿¿, of 157 ±

20 ps for a good fit. For CsPbBr3 NCs, a trion decay component with a lifetime of ~200 ps, in

addition to a biexciton decay component with a 40 ps lifetime, has been previously observed. 15

Trions can form when a charge remains trapped for a sufficiently long time such that its

geminate charge combines with an exciton created by the absorption of a photon during a

subsequent excitation pulse, producing a charged exciton. This is more likely to happen for

⟨ N ⟩>1 since that reduces the time between photon absorption events for a particular NC to its

minimum value i.e. the interval between excitation pulses. At significantly lower⟨ N ⟩ values, an

individual nanocrystal will not, on average, absorb a photon during every excitation pulse. Trions

have been observed in perovskite NCs to form even under sample stirring conditions under high

excitation fluences. 15

As in the case of neutral multiexcitons, the decay of trions in QDs is dominated by Auger

recombination. For a negative trion, this can be described in terms of Coulomb scattering

between the two conduction-band electrons, where one of them recombines with the hole in the

valence band while its energy is transferred to the other electron which is excited higher in the

conduction band. The similar process for a positive trion involves the Coulomb scattering of the

two valence band holes. Theoretically, the ratio of Auger recombination lifetimes between trions

and biexcitons has been calculated to be 4 for QDs with mirror-symmetric conduction and

15

valence bands. 23 However, from experimental measurements it has been found to be around 5

for CsPbBr1.5I1.5 and CsPbBr3 NCs. 14,15 In our case, the ratio obtained using the lifetimes

extracted from the CsPbCl3 transients is ~8. This deviation from the theoretical prediction has

been attributed to the possible asymmetries in the positive and negative trions pathways in this

type of NCs. 14 PL intermittency has been associated with the fluctuation between neutral single

excitons (ON state) and trions (OFF state) arising from pump-induced photoionization in

perovskite NCs, where the fraction of time the NC stays in the OFF state increases with

increasing pump intensity. 8 This reduces emission efficiencies and is unfavorable for many

applications. 14

Figure 4a shows the time-evolution of the near band edge transient spectra of the CsPbCl3

sample at⟨ N ⟩ ≪1. Here, the spectral dynamics at early delay times are product of the interaction

between the hot photogenerated exciton (created by the pump pulse) as it cools to the band edges

and the exciton created by the probe pulse. This biexciton effect is responsible for the observed

derivative-like shape of the spectra. In this figure, the photoinduced absorption peak at 3.01 eV

(412 nm) is labelled as A while the absorption bleach peak at 3.07 eV (403 nm) is denoted as B.

The fact that a photoinduced feature appears at the low-energy side of the absorption bleach

indicates an attractive exciton-exciton interaction. The magnitude of this interaction energy can

be calculated form the ratio between the amplitudes of these two peaks, i.e. A/B, which in this

case yielded a value A/B = 0.24, corresponding to an exciton-exciton interaction energy ∆XX of

10 ± 2 meV. 14,24 Very similar values of 12 meV and 11 meV have been reported previously for

CsPbI3 and CsPbBr1.5I1.5 NCs, respectively, using the same technique. 14 Exciton-exciton

interaction energies calculated by this method had shown no dependence with nanocrystal size.

16

However, when calculated from fluence-dependent time-resolved PL spectra, the∆XXvalues

obtained for CsPbI3 and CsPbBr3 NCs are larger, up to 100 meV, and show size dependency. 16,24

Over time (figure 4b), the bleach and photoabsorption features show complementary growth

and decay behaviors, respectively as the band edge state is filled by the intraband relaxation of

the hot carriers. Mono-exponential fitting to both of these transients gave an intraband cooling

lifetime τ cooling= 290 ± 37 fs. This also agrees with the reported values for CsPbI3 and CsPbBr3 by

Makarov et al. 14 These fast cooling rates are in agreement with the efficient channeling of hot

carriers to the emitting energy states observed from PLE measurements on CsPbI3, CsPbBr3 and

CsPbCl3 NCs. 25

Figure 4. a) Spectral dynamics at early delay times for ⟨N⟩ <<1; A and B indicate the amplitudes

of the absorption and bleach features, respectively. b) Transient change in absorption showing

the complementary behavior of both features and the fit to extract the cooling time constant.

17

CONCLUSIONS

In this work, we have studied the optical properties and charge carrier dynamics of all-

inorganic CsPbCl3 perovskite NCs. The values obtained for absorption cross-section, exciton-

exciton interaction energy and the lifetimes for single exciton trapping, biexciton and trion

recombination, radiative recombination and intraband cooling are all consistent with previously

reported values in that they follow the trend with decreasing mass of the halide ion observed by

others. As in other types of NC, radiative emission is limited by trap and Auger-mediated

recombination processes. Our experiments under variable pump fluences demonstrate the

dependency of the emission intensity on the charge dynamics at different excitation regimes and

the importance of the trap saturation process in reaching high quantum efficiencies. The key role

of trapping in our studies is consistent with very recent publications20,21 which report how

higher PLQY can be obtained by the use of suitable capping ligands, core/shell structures or

postsynthetic surface treatments to effectively passivate surface states.

ASSOCIATED CONTENT

AUTHOR INFORMATION

Corresponding Author

*Dr. David Binks, School of Physics and Astronomy and Photon Science Institute, The

University of Manchester. Email: david.binks@manchester.ac.uk

Author Contributions

The manuscript was written through contributions of all authors. All authors have given approval

to the final version of the manuscript.

18

ACKNOWLEDGMENT

Transient absorption measurements were performed at the Ultrafast Biophysics Facility,

Manchester Institute of Biotechnology, as funded by BBSRC Alert14 Award BB/M011658/1.

R.A-L. and J.A.A. thank CONACYT for provision of the scholarships 284566/399936 and

560774/293657, respectively. The data associated with this paper are openly available from

Mendeley data: DOI: 10.17632/ntjv58s9pj.1

SUPPORTING INFORMATION FOR PUBLICATION

The Supporting Information is available free of charge on the ACS Publications website.

Nano-cathodoluminescence (nano-CL) analysis and size distribution histogram; Excitation

dependence of the photoluminescence efficiency and data from a solution of CsPbCl3

nanocrystals; Transient absorption (TA) measurements, experimental details and additional

measurements; Fluence dependent Transient photoluminescence (TPL) measurements.

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