A recent study conducted by Ghosh, Marjit, Ghosh, and Patra sheds light on the potential for anisotropic-shaped CsPbBr3 perovskite nanocrystals (NCs) in optoelectronic applications. The study, titled “Hot Carrier Cooling and Biexciton Dynamics of Anisotropic-Shaped CsPbBr3 Perovskite Nanocrystals,” explores the hot carrier (HC) cooling and bi-exciton dynamics in hexapod and cube-shaped CsPbBr3 NCs using ultrafast transient absorption (TA) spectroscopy.
Key Outcomes:
- Prolonged HC cooling time and bi-exciton lifetime observed in hexapod CsPbBr3 NCs compared to cube-shaped NCs.
- Delocalization of charge carriers in shallow trap states leads to reduced overlap of electron and hole wave functions, which suppresses the bi-exciton AR rate.
- The study provides a toolbox for engineering HC cooling and bi-exciton lifetimes of LHP NCs, which could be helpful in optoelectronic applications.
The study prepared monodispersed cube and hexapod CsPbBr3 NCs by following previously reported hot-injection protocols with minor modifications. The TEM images of the cube and hexapod NCs, having an average edge length of 13 ± 1 nm and 50 ± 5 nm, respectively, were analyzed. The absorption cross-section values for the cube and hexapod were found to be 3.1 × 10^14 cm^2 and 5.2 × 10^14 cm^2, respectively, and were used to calculate the N. The bi-exciton AR lifetime in these hexapod NCs was measured using previously established methods.
The results revealed a prolonged HC cooling time of 650 fs for hexapod CsPbBr3 NCs compared to cube CsPbBr3 NCs, which had an HC cooling time of 354 fs. Further measurements of the HC temperature and intrinsic phonon decay time confirmed the slower HC cooling rate in hexapod NCs. Additionally, the bi-exciton lifetime of approximately 113 ps was observed for the hexapod, whereas it was around 45 ps for the cube.
The study highlights the potential for anisotropic-shaped CsPbBr3 perovskite nanocrystals in optoelectronic applications. The prolonged HC cooling time and bi-exciton lifetime observed in hexapod NCs provide a toolbox for engineering HC cooling and bi-exciton lifetimes of LHP NCs, which could be helpful in improving solar-energy efficiency.
Hot Carrier Cooling and Biexciton Dynamics of Anisotropic-Shaped CsPbBr 3 Perovskite Nanocrystals
Ghosh; Marjit; Ghosh; Patra
Full-text link: https://doi.org/10.1021/acs.jpcc.3c01441
What this paper is about
- In general, slow HC cooling is better suited for hot carrier-based solar cell applications, whereas fast HC cooling is required for efficient LED applications.21 HC cooling dynamics is mostly tuned by a variation of the composition, dimensionalities, formations of heterostructures, and impurity ion doping.
- Importantly, all of these unique shapes have been found to exhibit new facets that are exposed on the surface, providing a way to manipulate the photophysics of these materials.
- Additionally, the delocalization of charge carriers in the shallow trap states leads to a reduced overlap of electron and hole wave functions, which is evident from the high bi-exciton lifetime in the hexapod NCs.
What you can learn
- IACS Researchers have prepared monodispersed cube and hexapod CsPbBr 3 NCs by following previously reported hot-injection protocols with minor modifications.b shows the TEM images of the cube and hexapod CsPbBr 3 NCs, having an average edge length of 13 1 nm and 50 5 nm, respectively.
- The researcher’s analysis suggests that the retarded decay of hot LO phonon slows down the overall cooling dynamics of the HC in the hexapod CsPbBr 3 NCs.
- Notably, the absorption cross-section value is found to be 3.1 10 14 cm 2 and 5.2 10 14 cm 2 for the cube and hexapod, respectively, and these values are used to calculate the N. IACS researchers measured the biexciton AR lifetime in these hexapod NCs by following the previously reported well-established methods.
- The overview of hot carrier cooling and biexciton dynamics for cube and hexapod CsPbBr 3 NCs is presented in Scheme 1.
- The results reveal the prolonged HC cooling time for hexapod CsPbBr 3 NCs compared to cube CsPbBr 3 NCs.
- Further measurements of the HC temperature and intrinsic phonon decay time unequivocally confirm the slower HC cooling rate in hexapod NCs.
Core Q&A related to this research
What is the purpose of the study discussed in the paper?
A: The purpose of the study is to investigate the hot carrier cooling and biexciton dynamics of anisotropic-shaped CsPbBr3 perovskite nanocrystals, specifically comparing cube and hexapod shapes.
What is the significance of the different cooling rates in hot carrier-based solar cell and LED applications?
A: Slow hot carrier cooling is better suited for hot carrier-based solar cell applications, while fast hot carrier cooling is required for efficient LED applications.
How were the cube and hexapod CsPbBr3 NCs prepared?
A: The researchers prepared monodispersed cube and hexapod CsPbBr3 NCs by following previously reported hot-injection protocols with minor modifications.
What is the absorption cross-section value for the cube and hexapod CsPbBr3 NCs?
A: The absorption cross-section value is found to be 3.1 × 10^14 cm^2 and 5.2 × 10^14 cm^2 for the cube and hexapod, respectively.
How do the results of the study suggest that the bi-exciton AR rate can be significantly suppressed in hexapod NCs?
A: The delocalization of charge carriers in the shallow trap states leads to a reduced overlap of electron and hole wave functions, which is responsible for suppressing the bi-exciton AR rate. Additionally, the bi-exciton lifetime is observed to be approximately 113 ps for the hexapod, while it is ∼45 ps for the cube.
Basic Q&A related to this research
What is hot carrier cooling?
Hot carrier cooling is the process by which the energy of a “hot” charge carrier (an electron or a hole with excess energy) is dissipated through thermal relaxation to the surrounding environment.
What is biexciton dynamics?
Biexciton dynamics is the study of the interactions between two excitons (electron-hole pairs) in a material, and how they affect the material’s optical and electronic properties.
What are anisotropic-shaped CsPbBr3 perovskite nanocrystals?
Anisotropic-shaped CsPbBr3 perovskite nanocrystals are tiny crystals made of cesium lead bromide perovskite with irregular shapes that exhibit different physical and optical properties than their cubic counterparts.
What is a hexapod?
A hexapod is a six-legged structure or object, such as a nanocrystal with six arms.
What are solar cells?
Solar cells are devices that convert sunlight into electrical energy using the photovoltaic effect.
What are dimensionalities?
Dimensionalities refer to the number of dimensions or spatial arrangements of a material or object.
What are heterostructures?
Heterostructures are materials composed of two or more different semiconductor materials with different crystal structures.
What is impurity ion doping?
Impurity ion doping is the process of intentionally introducing foreign atoms or ions into a semiconductor material to change its electrical or optical properties.
What is photophysics?
Photophysics is the study of the interactions between light and matter, including how light is absorbed, emitted, and scattered by materials.
What are charge carriers?
Charge carriers are particles (such as electrons or holes) that can carry an electrical charge through a material.
What are shallow trap states?
Shallow trap states are energy levels in a material that are close to the energy of the charge carriers, allowing them to become trapped or delayed.
What is an electron wave function?
An electron wave function describes the probability of finding an electron at a specific location in a material.
What is a hole wave function?
A hole wave function describes the probability of finding an empty electron state (a “hole”) at a specific location in a material.
What is absorption cross-section?
Absorption cross-section is a measure of the probability that a photon of a specific energy will be absorbed by a material.
What is femtosecond TA spectroscopy?
Femtosecond TA (transient absorption) spectroscopy is a technique that uses short pulses of light to study ultrafast dynamics in materials, such as the interactions between light and charge carriers.
What is Auger recombination?
Auger recombination is a process by which a charge carrier loses its excess energy by transferring it to another carrier in the material.
What are solar absorbers?
Solar absorbers are materials that absorb sunlight and convert it into usable energy, such as in solar cells.
What is lead halide perovskite?
Lead halide perovskite is a type of material that has shown great promise in high-performance solar cells due to its unique properties and high efficiency.
What are isotropic cubic shapes?
Isotropic cubic shapes are regular three-dimensional shapes with equal dimensions in all directions.
[…] […]