Halide Perovskite

1. Journal
Study
Size- and Halide-Dependent Auger Recombination in Lead Halide
Perovskite Nanocrystals
Yulu Li, Xiao Luo, Tao Ding, Xin Lu, and Kaifeng Wu*
-By Andi
 Halide perovskite nanocrystal
 Auger recombination
 The effect of size and component
differences

2. Halide Perovskite
 Halide perovskite is a group of semiconductor materials consisting of ABX3
compounds consisting of halide metal and organic or inorganic cationic ions.
ABX3
A : Methylammonium, Formamidinium (FA), Cesium (Cs)
B : Stannum (Sn) or Plumbum (Pb)
X : Iodide (I), Bromide (Br), or Chloride (Cl) →Halide Metal
 Advantages:
 High solar energy conversion efficiency
 Ease of synthesis
 Interesting optical properties
 Applications:
 Solar cells
 LED
 Transistor
 Photodetector
“However, due to the material's inadequate stability,
research continues to develop more stable and
environmentally friendly halide perovskites in
optoelectronic applications”
This research use APbX3 (A=Cs and FA; X=Cl, Br, and I)
[CsPbCl3; CsPbBr3; CsPbI3; and FAPbBr3, ]
But poor stability and toxic chemicals in its synthesis.
Introduction

3. Introduction
Halide perovskite nanocrystals (NCs) hold strong promise for a
variety of light-harvesting, emitting, and detecting applications, all
of which, however, could be complicated by multicarrier Auger
recombination.
What is Auger Recombination?
Auger recombination is a non-radiative process where the excess energy
from the electron-hole recombination is transferred to electrons or holes
that are subsequently excited to higher energy states within the same band
instead of giving off photons (the radiative process).
“it leads to the loss of energy that could otherwise be converted into
electrical current.”
Obstacl
e
The multicarrier Auger recombination (AR), whereby the recombination
energy of an electron–hole pair is not released as a photon but rather is
absorbed by a third carrier or another exciton Investigate the size- and composition-dependent
biexciton AR lifetimes
This Research

4. APbX3 NCs were synthesized by hot-injection methods
Schematic of the hot injection method
T = 140 – 200 ⁰C
The samples were placed in 1 mm cuvettes and
were vigorously stirred in all the measurements
TA experiment
Probe Beam
(white light continuum)
Pump Beam
(350-500 nm)
Samples were vigorously stirred during
the measurements to avoid sample
damaging.
Nanocrystal Preparation
Experimental Method
1
2
Size control by
 Change temperature
 Different Halide component

5. Result
Figure 1 shows the UV/Vis absorption and photoluminescence (PL) spectra
of NCs of varying size and composition dispersed in hexane.
• The PL peaks were correspondingly shifted with the absorption peaks
• as the size of the nanocrystal decreases, the absorption wavelength gets
smaller.
Quantum Confinement Effect
https://www.researchgate.net
Figure 1. UV/Vis absorption (colored lines) and PL spectra (dashed
lines with shadings)

6. The Photoluminescence quantum yield or PLQY of a molecule or
material is defined as the number of photons emitted as a fraction of
the number of photons absorbed.
PLQY is a ratio of the number of photons emitted by the sample
compared to the number of photons absorbed by the sample, expressed
as a percentage.
The result in this paper show PLQY around 30–80%
The higher the PLQY value, the more efficient the sample is in producing emitted light.
Result
Photoluminescence quantum yield

7. Result
Figure 2. a) TA kinetics probed at the exciton bleach with varying pump
intensities b) Biexciton recombination kinetics of varying sizes
 The XB kinetics measured at varying pump
intensities can be normalized to the long-lived tail
after approximately 200 ps.
 A fast decay component whose amplitude grows
rapidly with the pump intensity, which is a typical
manifestation of multiexciton recombination
Figure 2a
Figure 2b
Figure 3
 Decay occurs very quickly for smaller nanocrystal
sizes ?
Figure 3a
AR lifetimes (𝜏𝑥𝑥) Vs Nanocrystal Volume
𝜏𝑥𝑥 = 𝜷𝑉
 AR is virtually independent the cation
composition
 AR depends sensitively on the halide
composition
ABX3
Cation
Anion

8. This research use APbX3 (A=Cs and FA; X=Cl, Br, and I)
[CsPbCl3; CsPbBr3; CsPbI3; and FAPbBr3, ]
ABX3
Cation
Anion
not significant differences
Different Cation-same Anion
Same Cation-Different Anion
significant differences
Result

9. • The scaling coefficient is virtually independent of the cation but rather depends sensitively on the anion.
• The Auger lifetime of all NCs scales linearly with NC volume.
• The volume scaling coefficients determined in this study enable facile estimation of Auger
recombination rates, which are key parameters to be considered in perovskite NC-based devices
Conclution
𝜏𝑥𝑥 = 𝜷𝑉
Question
 what does it mean that the decay happens very fast (when the delay time is small)?

10. Terima Kasih
ありがとうございました

11. Why?
This process can occur when the carrier density in the
semiconductor is very high, causing electrons and holes
to collide and reduce the carrier lifetime.
Dalam perovskite, struktur kristal terdiri dari ion logam positif atau kation dan ion anion negatif.
Komponen kation dalam perovskite material umumnya memiliki efek yang lebih kecil pada reaksi Auger
karena mereka tidak memiliki orbital p kosong yang memungkinkan interaksi dengan orbital p dari
anion. Oleh karena itu, mereka tidak menyebabkan peningkatan kepadatan keadaan di dekat celah
energi (bandgap) perovskite.
Namun, komponen anion mempengaruhi Auger recombination karena mereka memiliki orbital p yang
dapat berinteraksi dengan orbital p lainnya, menyebabkan terjadinya hibridisasi dan peningkatan
kepadatan keadaan di dekat celah energi. Peningkatan kepadatan keadaan ini mempengaruhi reaksi
Auger karena meningkatkan kemungkinan interaksi antara muatan listrik, yang dapat menyebabkan
Auger recombination terjadi dengan lebih efektif.
Selain itu, komponen anion dalam perovskite material dapat mempengaruhi stabilitas material dan
perpindahan muatan elektron karena mereka berinteraksi dengan lingkungan kimia sekitarnya. Hal ini
dapat mempengaruhi kinerja perovskite dalam aplikasi fotovoltaik dan mempengaruhi efisiensi konversi
energi yang dihasilkan oleh sel surya perovskite.