Power Dependent Hot Carrier Cooling Dynamics in Trioctylphosphine Capped CsPbBr<sub>3</sub> Perovskite Quantum Dots Using Ultrafast Spectroscopy

Jain

et al. 2023

ACS Appl. Nano Mater.

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Slow cooling and long-lived hot carrier (HC) population plays a crucial role in crossing the Shockley–Queisser limit and achieving high-efficiency perovskite photovoltaic devices up to 66%. Herein, we investigated the slow cooling of HCs via charge transfer in in-situ synthesized CsPbBr3 perovskite quantum dots-decorated graphitic carbon nitride nanosheet (CsPbBr3 PQDs/g-CN NS) heterostructures using ultrafast transient absorption (UTA) spectroscopy. Halide perovskites showed excitation energy-dependent HC cooling. We examined the HC dynamics at two different excitation energies with varying excitation pump fluences. UTA revealed significantly higher slow cooling and slow bleach recovery in CsPbBr3 PQDs/g-CN NSs (i.e., 632 fs and 845 ps) compared to pure CsPbBr3 PQDs (i.e., 512 fs and 371 ps) at an excitation energy of 3.54 eV and a fluence of 250 μW, suggesting that HCs transfer through the heterostructure interface. The observed slow cooling can be explained by the stronger interaction between the organic polymeric frameworks of g-CN NSs and CsPbBr3 PQDs, which passivates the trap states of CsPbBr3 PQDs and offers slow electron–hole recombination by slowing down the Auger recombination or the hot-phonon bottleneck effect. Additionally, density functional theory (DFT) calculations were carried out to shed light on band alignment at the interface to reveal the mechanism of efficient charge transfer in CsPbBr3 PQDs/g-CN NSs and validate the experimental findings. The insight of this study is quite beneficial for designing modified perovskite nanostructures for realization in perovskite solar cells in the near future.

Section: Resultsmentioning

confidence: 99%

Slow Cooling and Transfer Dynamics of Hot Excitons in CsPbBr₃ Perovskite Quantum Dots/g-CN Nanosheet Heterostructures: Implications for Optoelectronic Applications

Jain

et al. 2023

ACS Appl. Nano Mater.

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“…TRPL decay's shorter and longer life has been vividly studied and reported earlier. 39,40 The fast component τ 1 suggests fast electron transfer at the interface indicating a nonradiative transition, and the slow component τ 2 provides evidence of the radiative transition. The fast nonradiative lifetime τ 1 (1.98 ns) is ascribed to transfer of band edge electrons from CsPbBr 3 PNCs to ZnO in CsPbBr 3 /ZnO heterostructures.…”

Section: Optical Properties' Study Using Steady-state and Ultrafast M...mentioning

confidence: 99%

Insight into Hot Carrier Kinetics of CsPbBr₃/ZnO Heterostructures for Photodetector Application

Rahman

et al. 2023

ACS Appl. Opt. Mater.

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Understanding the hot carrier kinetics in heterostructures of inorganic halide perovskite nanocrystals (PNCs) and extraction of the excess energy of hot-carriers is crucial for their future emergence in optoelectronic devices. Herein, CsPbBr 3 /ZnO heterostructures have been prepared via the most adopted in situ hot-injection method, and ZnO nanoparticles were obtained by a simple chemical process. We have investigated the carrier transfer dynamics through steady-state and ultrafast optical measurements. Steady-state measurements (i.e., photoluminescence and time-resolved photoluminescence decay) reveal that electron transfer from PNCs to surface-attached ZnO nanoparticles is the most probable transition process that happened in heterostructured systems. Furthermore, deep insights into the charge transfer kinetics were investigated by performing ultrafast transient absorption (UTA) spectroscopy at two varying pump fluences (i.e., 0.40 and 0.20 mW) with an excitation wavelength of 450 nm. UTA analysis reveals a significant slow hot carrier cooling at 0.40 mW fluence (from 670 fs to 1.56 ps) and 0.20 mW (from 480 fs to 1.23 ps) in CsPbBr 3 /ZnO heterostructure systems, suggesting reduced exciton recombination and high charge-carrier transfer through the heterostructure interface. The efficient charge extraction in CsPbBr 3 /ZnO results in a measurable change in photodetector responsivity and detectivity. This study provides an understanding of the hot carrier kinetics of metal halide perovskites CsPbBr 3 /ZnO for optoelectronic device applications.

“…Heretofore, a large number of spintronic materials have been investigated, including europium chalcogenides (EuO and EuS), spinel (NiFe 2 O 4 and CoFe 2 O 4 ), , perovskite oxides (BiFeO 3 ), double perovskite oxides (Bi 2 CrOsO 6 ), − Heusler compounds (CoVTiAl and CoVZrAl), and layered Cr-based materials, as well as CrGeTe 3 and CrI 3 . Their tiny number of spin-polarized carriers and low Curie temperature are two major roadblocks for establishing room-temperature (RT) spintronics. , Their exceptional optoelectronic capabilities , make light-emitting lead metal halide perovskite (LMHP) nanocrystals (NCs) a stronger contender for solar energy harvesting, e.g., including their high carrier mobility, low trap density, large extinction coefficient, large carrier diffusion length, long carrier lifetime, and tunable bandgap . LMHPs NCs, also known as nanocrystal quantum dots (QDs), have gained a leading position within the portfolio of compounds as a new generation of solution-processed semiconductors.…”

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confidence: 99%

“…9 Their tiny number of spin-polarized carriers and low Curie temperature are two major roadblocks for establishing room-temperature (RT) spintronics. 1,6 Their exceptional optoelectronic capabilities 10,11 make light-emitting lead metal halide perovskite (LMHP) nanocrystals (NCs) a stronger contender for solar energy harvesting, e.g., including their high carrier mobility, low trap density, large extinction coefficient, 12 large carrier diffusion length, long carrier lifetime, 13 and tunable bandgap. 14 LMHPs NCs, also known as nanocrystal quantum dots (QDs), 15 have gained a leading position within the portfolio of compounds as a new generation of solution-processed semiconductors.…”

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confidence: 99%

“…14 LMHPs NCs, also known as nanocrystal quantum dots (QDs), 15 have gained a leading position within the portfolio of compounds as a new generation of solution-processed semiconductors. The material properties mentioned above are intensely pursued to ensure superperformance in classical light sources incorporating solar cells, 16 light-emitting diodes (LEDs), 11 liquid crystal display (LCD) technologies, 17 ultraviolet−visible−near-infrared (UV−vis−NIR) photodetectors, 18 direct conversion X-ray and γ-ray detectors, 19 scintillators, 20,21 quantum light sources, 22 photodetectors, 23 optical communication, 24 singlephoton sources, 24,25 etc.…”

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confidence: 99%

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Lattice-Distortion-Induced Change in the Magnetic Properties in Br-Defect Host CsPbBr₃Perovskite Quantum Dots

Chauhan

et al. 2023

J. Phys. Chem. Lett.

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Herein, we report temperature-and field-induced magnetic states in CsPbBr 3 perovskite quantum dots (PQDs) attributed to Br defects. We find that temperaturedependent structural distortion is the main source of various temperature-induced magnetic states in Br-defect host CsPbBr 3 PQDs. Comprehensively examined magnetization data through Arrott plots, Langevin and Brillouin function fitting, and structural analysis reveal the presence of various oxidation states (i.e., Pb 0 , Pb + , Pb 2+ , and Pb 3+ ) yielding different magnetic states, such as diamagnetic states above 90 K, paramagnetic states below ≈90 K, and perhaps locally ordered states between 58 and 90 K. It is realized from theoretical fits that paramagnetic ions exist (i.e., superparamagnetic behavior) due to Br defects causing Pb + (and/ or Pb 3+ ions) in the diamagnetic region. We anticipate that our findings will spur future research of the development of spin-optoelectronics, such as spin light-emitting diodes, and spintronics devices based on CsPbBr 3 PQDs.