Hot Carrier Transfer Research Articles

Hot carrier transfer from plasmon decay in Ag20at H-Si(111) surface: real-time TDDFT simulation in Wannier gauge.

Plasmon decay is believed to play an essential role in inducing hot carrier transfer at the interfaces between plasmonic nanoparticles and semiconductor surfaces. In this work, we employ real-time time-dependent density functional theory (RT-TDDFT) simulation in the Wannier gauge to gain quantum-mechanical insights into the nonlinear dynamics of the plasmon decay in the Ag20nanoparticle at a semiconductor surface. The first-principles simulations show that the plasmon decay is more than two times faster when the Ag20nanoparticle is adsorbed on a hydrogen-terminated Si(111) surface, taking place within 100 femtoseconds of the plasmon excitation. Hot carrier transfer across the interface is observed as the plasmon decay takes place, and nearly 30% of holes are generated deep in the valence band of the semiconductor surface. The use of Wannier gauge in RT-TDDFT simulation is particularly convenient for gaining quantum-mechanical insights into non-equilibrium electron dynamics in complex heterogeneous systems.

(Invited) Plasmon Induced Hot Electron Transfer from Doped Semiconductor Nanocrystals

In recent years, a new class of plasmonic materials based on doped semiconductor NCs has been developed. Similar to noble metals, localized surface plasmon resonances in doped semiconductor NCs arises from the coherent collective oscillation of free carriers within the NCs. The wide tunability of free carrier concentration results in tunable plasmon bands spanning from the visible to mid-infrared regime and these plasmonic semiconductor NCs have been reported to drive plasmonic hot carrier photocatalysis under near IR light illumination. These reports suggest that plasmonic semiconductors is an interesting material platform for efficient near IR driven hot carrier photocatalysis. So far the reported efficiencies are low and the mechanisms of hot carrier generation, transfer and recombination are unclear. There are interesting similarities and differences between metal and semiconductor plasmonics. First, plasmons in semiconductors can decay by inter- (band gap) and intra- band plasmon decay. Furthermore, charge transfer transition in semiconductor heterostructures have been extensively reported; can plasmon decay in plasmonic-semiconductor/semiconductor junctions proceed by exciting interfacial ET across the junction, similar to the PICTT pathway reported for metal/semiconductor junctions? Second, in plasmonic semiconductor materials, where there is a lack of states within the p-semiconductor bandgap, the transferred electrons in the accepting semiconductor CB can recombine only with the VB holes in the plasmonic semiconductor. This process requires dissipation of ~ >1 eV energy, which may slow down the recombination rate. In this talk, I will discuss our recent progresses in studying plasmon induced hot electron transfer and recombination in plasmonic semiconductor/semiconductor interfaces.

On-Surface Photopolymerization - What Does the Surface Do?

We attained the synthesis of mesoscale-ordered 2D polymers by the topochemical on-surface photopolymerization of fluorinated anthracene triptycene (fantrip) monomers. The underlying protocol is two-staged: (1) Self-assembly of the monomers into a photopolymerizable monolayer structure, where the photoactive anthracene moieties are face-to-face stacked; (2) cross-linking of the self-assembled monolayer into a covalent 2D polymer by photochemically excited [4+4] cycloadditions between the antiparallel aligned anthracene blades. Thereby, the long-range order attained in step (1) is transferred into the covalent state.Yet, the topochemical approach depends crucially on achieving the reactive monomer packing with the appropriate mutual alignment of the anthracene blades. For this initial self-assembly, the underlying surface plays a decisive role, which also extends to the photopolymerization.We show that the photoactive monolayer packing of fantrip monomers can be achieved on both alkane-passivated graphite and iodine-passivated Au(111) or Ag(111). Although the fantrip self-assembly appears essentially similar on these substrates, there are distinct differences in the subsequent photopolymerization. These can be rationalized by the photoexcitation of the substrate and the subsequent transfer of hot carriers to the molecular networks.Nat. Chem. 13, 730-736 (2021)Eur. J. Org. Chem. 2021, 5478–5490 (2021)Trends Chem. 4, 471-474 (2022)Angew. Chem. Int. Ed. 61, e202201044 (2022)

(Invited) Unraveling Hot Carrier Transfer Processes in Plasmonic Catalysis

In the last decade, plasmonic nanoantennas have revolutionized light manipulation and control at the nanoscale. Interestingly, generation of hot carriers in metals upon light absorption have opened new pathways for controlling photo(electro)chemical processes and engineering photocatalysts. Yet, fundamental questions remain about the microscopic details of these complex light-matter interactions.We have recently developed a well-controlled platform for micro-scale plasmonic photoelectrochemistry studies that leverages the unique properties of monocrystalline microflakes [1] as well as precise nanofabrication methods. Interestingly, the microflakes exhibit well-defined crystal facets and can bridge the properties of bulk metals with those of nanoscale plasmonic antennas, accessing ultra-thin film dimensions (sub 15-nm) that are challenging for polycrystalline films. By performing careful absorption measurements, we explore the photoelectrochemical performance of these hot carrier micro-scale photoelectrodes for inner- and outer-sphere reactions [2], concurrently comparing them to cm-scale devices [3]. This allows us to unravel the interplay of hot carrier generation and transport at metal-liquid and metal-semiconductor interfaces and identify bottlenecks for charge transfer.[1] Kiani F., Tagliabue G. - High‐Aspect Ratio Au Microflakes via Gap‐Assisted Synthesis – Chemistry of Materials 34 (3), 1278-1288, 2022[2] Kiani F. et al - Transport and Interfacial Injection of d-band Hot Holes Control Plasmonic Chemistry - ACS Energy Letters, 8 (10), 4242-4250, 2023[3] Ma J., Oh K., Tagliabue G. - Understanding Wavelength-Dependent Synergies between Morphology and Photonic Design in TiO2-Based Solar Powered Redox Cells – Journal of Physical Chemistry C, 127 (1), 11-21, 2022

Plasmonic Hot Carrier‐Driven Photoelectrochemical Processes: Principle, Detection and Application

AbstractUtilizing hot carriers induced by surface plasmon resonance in solar energy conversion to chemical fuels is a crucial issue in the field of photocatalysis. To achieve practical efficiency in plasmonic hot carrier application to photocatalysts, it is essential to theoretically and experimentally understand the generation, relaxation, and transfer of hot carriers. Photoelectrochemical (PEC) processes can offer a pathway to investigate the transfer dynamics of hot electrons (or hot holes) and enhance the efficiency of both hot carrier transfer and catalytic activity. This work summarizes a theoretical and experimental understanding of the hot carrier effect, emphasizing the hot carrier transfer dynamics to investigate the exact role of hot carriers in PEC reactions. The principles of hot carrier detection, diverse applications of hot carrier‐based photocatalysis, and perspectives for possible future progress are discussed.

Hot‐carrier engineering for two‐dimensional integrated infrared optoelectronics

AbstractPlasmonic hot carrier engineering holds great promise for advanced infrared optoelectronic devices. The process of hot carrier transfer has the potential to surpass the spectral limitations of semiconductors, enabling detection of sub‐bandgap infrared photons. By harvesting hot carriers prior to thermalization, energy dissipation is minimized, leading to highly efficient photoelectric conversion. Distinguished from conventional band‐edge carriers, the ultrafast interfacial transfer and ballistic transport of hot carriers present unprecedented opportunities for high‐speed photoelectric conversion. However, a complete description on the underlying mechanism of hot‐carrier infrared optoelectronic device is still lacking, and the utilization of this strategy for tailoring infrared response is in its early stages. This review aims to provide a comprehensive overview of the generation, transfer and transport dynamics of hot carriers. Basic principles of hot‐carrier conversion in heterostructures are discussed in detail. In addition, progresses of two‐dimensional (2D) infrared hot‐carrier optoelectronic devices are summarized, with a specific emphasis on photodetectors, solar cells, light‐emitting devices and novel functionalities through hot‐carrier engineering. Furthermore, challenges and prospects of hot‐carrier device towards infrared applications are highlighted.image

Plasmon-Induced Ultrafast Hot Hole Transfer in Nonstoichiometric CuxInyS/CdS Heteronanocrystals.

Plasmonic semiconductors are promising candidates for developing energy conversion devices due to their tunable band gap, cost-effectiveness, and nontoxicity. Such materials exhibit remarkable capabilities for harvesting infrared photons, which constitute half of the solar energy spectrum. Herein, we have synthesized near-infrared (NIR) active CuxInyS nanocrystals and CuxInyS/CdS heterostructure nanocrystals (HNCs) to investigate plasmon-induced charge transfer dynamics on an ultrafast time scale. Employing femtosecond transient absorption spectroscopy, we demonstrate that upon exciting the HNCs with sub-band gap NIR photons (λ = 840 nm), the hot holes are generated in the valence band of plasmonic CuxInyS and transferred to the adjacent semiconductor. The decreased signal intensity and accelerated hole phonon relaxation dynamics for HNCs reveal efficient transfer of plasmon-induced hot carriers from CuxInyS to CdS under both 840 and 350 nm laser excitations, providing a pathway for enhanced carrier utilization. These findings shed light on the potential of ternary chalcogenides in plasmonic applications, highlighting efficient hot carrier extraction to adjacent semiconductors.

Upconversion electroluminescence in 2D semiconductors integrated with plasmonic tunnel junctions.

Plasmonic tunnel junctions are a unique electroluminescent system in which light emission occurs via an interplay between tunnelling electrons and plasmonic fields instead of electron-hole recombination as in conventional light-emitting diodes. It was previously shown that placing luminescent molecules in the tunneling pathway of nanoscopic tunnel junctions results in peculiar upconversion electroluminescence where the energy of emitted photons exceeds that of excitation electrons. Here we report the observation of upconversion electroluminescence in macroscopic van der Waals plasmonic tunnel junctions comprising gold and few-layer graphene electrodes separated by a ~2-nm-thick hexagonal boron nitride tunnel barrier and a monolayer semiconductor. We find that the semiconductor ground exciton emission is triggered at excitation electron energies lower than the semiconductor optical gap. Interestingly, this upconversion is reached in devices operating at a low conductance (<10-6 S) and low power density regime (<102 W cm-2), defying explanation through existing proposed mechanisms. By examining the scaling relationship between plasmonic and excitonic emission intensities, we elucidate the role of inelastic electron tunnelling dipoles that induce optically forbidden transitions in the few-layer graphene electrode and ultrafast hot carrier transfer across the van der Waals interface.

Enhancing perovskite solar cell performance: The role of polymer-assisted hole transport layers in hot carrier dynamics

Enhancing the efficiency and stability is very critical for perovskite solar cells (PSCs) commercialization. Herein, we report an effective approach to enable highly efficient and stable PSCs by incorporating a polymer material, poly[N, N′-bis(2-octyldodecyl)-naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5,5′-(2,2′-bithiophene) (named P(NDI2OD-T2)), into hole transport layer (HTL). Our research results exhibit that the addition of P(NDI2OD-T2) not only effectively improves the hole mobility and conductivity of HTL, but also makes its energy level more alignment with perovskite. More importantly, ultrafast carrier results demonstrate that the introduction of P(NDI2OD-T2) into Spiro-OMeTAD HTL can effectively improve the extraction and transfer of hot carriers from perovskite layer to HTL, and consequently reduce the recombination of charge carriers in the device. As a result, PSCs based on Spiro + P(NDI2OD-T2) as a HTL shows an enhanced power conversion efficiency (PCE) of 24.20 %, which is much higher than that of control device without P(NDI2OD-T2) (21.94 %). Furthermore, the un-encapsulated P(NDI2OD-T2)-treated PSCs exhibit excellent humidity, thermal and light stabilities, with the devices maintaining 94 % of its initial efficiency after 3000 h at ≈40 % humidity, 95 % of its initial efficiency after storage at 65 °C and 85 °C for 600 h, and 90 % of its initial efficiency after 600 h under one sun light irradiation, respectively. This work provides an effective strategy for improving the device efficiency and long-term stability of PSCs.

Three-atom-wide gold quantum rods with periodic elongation and strongly polarized excitons

Atomically precise control over anisotropic nanoclusters constitutes a grand challenge in nanoscience. In this work, we report our success in achieving a periodic series of atomically precise gold quantum rods (abbrev. Au QRs) with unusual excitonic properties. These QRs possess hexagonal close-packed kernels with a constant three-atom diameter but increasing aspect ratios (ARs) from 6.3 to 18.7, all being protected by the same thiolate (SR) ligand. The kernels of the QRs are in a Au1-(Au3)n-Au1 configuration (where n is the number of Au3 layers) and follow a periodic elongation with a uniform Au18(SR)12 increment consisting of four Au3 layers. These Au QRs possess distinct HOMO-LUMO gaps (Eg = 0.6 to 1.3 eV) and exhibit strongly polarized excitonic transition along the longitudinal direction, resulting in very intense absorption in the near-infrared (800 to 1,700 nm). While excitons in gapped systems and plasmons in gapless systems are distinctly different types of excitations, the strongly polarized excitons in Au QRs surprisingly exhibit plasmon-like behaviors manifested in the shape-induced polarization, very intense absorption (~106 M-1 cm-1), and linear scaling relations with the AR, all of which resemble the behaviors of conventional metallic-state Au nanorods (i.e., gapless systems), but the QRs possess distinct gaps and very long excited-state lifetimes (10 to 2,122 ns), which hold promise in applications such as near-infrared solar energy utilization, hot carrier generation and transfer. The observation of plasmon-like behaviors from single-electron transitions in Au QRs elegantly bridges the distinct realms of single-electron and collective-electron excitations and may stimulate more research on excitonics and plasmonics.

Auger‐Assisted Secondary Hot Carrier Transfer in a Type I MoS2/PtSe2 Heterostructure

AbstractCharge transfer is vital in determining the optoelectronic properties of atomically thin materials, yet remains elusive in type I heterostructures. Here, distinct two‐step charge transfer processes in a type I MoS2/PtSe2 heterostructure are reported. By exclusively exciting the smaller bandgap PtSe2, strong exciton photobleaching peaks of the larger bandgap MoS2 are observed, indicating primary hot carrier transfer from PtSe2 to MoS2 within 70 fs. More importantly, the amplitude of the exciton peaks shows a secondary increase after the initial rapid decay. These dynamics are distinctly different from the monotonic decrease in monolayer MoS2 and indicate a secondary charge transfer process that is attributed to hot carriers re‐generated in PtSe2 by intralayer Auger recombination. Concurrently, the exciton energy blue shifts within 100 ps, probing the dynamic buildup of a charge‐transfer induced electric field across the heterostructure interface, which displaces electron and hole wavefunctions of MoS2 excitons and reduces the exciton binding energy. The results are corroborated by carrier dynamics and transient absorption spectra simulations by considering the two‐step charge transfer processes. The work reveals Auger‐assisted hot carrier transfer processes in type I heterostructures and suggests the possibility for optoelectronic and photocatalytic applications by optical sub‐bandgap excitation.

Plasmon induced hot carrier distribution in Ag20 -CO composite.

The interaction between plasmons and the molecules leads to the transfer of plasmon-induced hot carriers, presenting innovative opportunities for controlling chemical reactions on sub-femtosecond timescales. Through real-time time-dependent density functional theory simulations, we have investigated the enhancement of the electric field due to plasmon excitation and the subsequent generation and transfer of plasmon-induced hot carriers in a linear atomic chain of Ag20 and an Ag20 -CO composite system. By applying a Gaussian laser pulse tuned to align with the plasmon frequency, we observe a plasmon-induced transfer of hot electrons from the occupied states of Ag to the unoccupied molecular orbitals of CO. Remarkably, there is a pronounced accumulation of hot electrons and hot holes on the C and O atoms. This phenomenon arises from the electron migration from the inter-nuclear regions of the C-O bond towards the individual C and O atoms. The insights garnered from our study hold the potential to drive advancements in the development of more efficient systems for catalytic processes empowered by plasmonic interactions.

Full-spectrum plasmonic semiconductors for photocatalysis.

Localized surface plasmon resonance (LSPR) of noble metal nanoparticles can focus surrounding light onto the particle surface to boost photochemical reactions and solar energy utilization. However, the rarity and high cost of noble metals limit their applications in plasmonic photocatalysis, forcing researchers to seek low-cost alternatives. Recently, some heavily doped semiconductors with high free carrier density have garnered attention due to their metal-like LSPR properties. However, plasmonic semiconductors have complex surface structures characterized by the presence of a depletion layer, which poses challenges for active site exposure and hot carrier transfer, resulting in low photocatalytic activity. In this review, we introduce the essential characteristics and types, synthesis methods, and characterization techniques of full-spectrum plasmonic semiconductors, elucidate the mechanism of full-spectrum nonmetallic plasmonic photocatalysis, including the local electromagnetic field, hot carrier generation and transfer, the photothermal effect, and the solutions for the surface depletion layer, and summarize the applications of plasmonic semiconductors in photocatalytic environmental remediation, CO2 reduction, H2 generation, and organic transformations. Finally, we provide a perspective on full-spectrum plasmonic photocatalysis, aiming to guide the design and development of plasmonic photocatalysts.

Strong-field effects in the photo-induced dissociation of the hydrogen molecule on a silver nanoshell.

Plasmonic catalysis is a rapidly growing field of research, both from experimental and computational perspectives. Experimental observations demonstrate an enhanced dissociation rate for molecules in the presence of plasmonic nanoparticles under low-intensity visible light. The hot-carrier transfer from the nanoparticle to the molecule is often claimed as the mechanism for dissociation. However, the charge transfer time scale is on the order of a few femtoseconds and cannot be resolved experimentally. In this situation, ab initio non-adiabatic calculations can provide a solution. Such simulations, however, have their own limitations related to the computational cost. To accelerate plasmonic catalysis simulations, many researchers resort to applying high-intensity external fields to nanoparticle-molecule systems. Here, we show why such an approach can be problematic and emphasize the importance of considering strong-field effects when interpreting the results of time-dependent density functional theory simulations of plasmonic catalysis. By studying the hydrogen molecule dissociation on the surface of a silver nanoshell and analyzing the electron transfer at different field frequencies and high intensities, we demonstrate that the molecule dissociates due to multiphoton absorption and subsequent ionization.

Tuning hot carrier transfer dynamics by perovskite surface modification

Understanding the role of perovskite surface passivators in hot carriers transfer dynamics is important to develop highly efficient perovskite solar cells (PSCs). In this work, we have designed and synthesized a naphthalimide-based organic small molecule (NCN) for perovskite surface defect passivator. We reveal that the introduction of NCN not only reduces the density of perovskite defect-state, but also promotes hot carriers (HCs) cooling in perovskite through the transient absorption spectroscopy measurements. Fast HCs cooling permits HCs transfer from perovskite layer into NCN layer, thus resulting in the decreased charge-carrier recombination in NCN-treated device. As expected, the power conversion efficiency (PCE) of PSCs with NCN is enhanced to 22.02% from 19.95% for the control device. The findings are relevant for developing highly efficient PSCs.

Interface-engineered Au@MoS2 core-shell heterostructures with superior hot-carrier transfer dynamics for plasmonics and optoelectronics

Interface-engineered Au@MoS2 core-shell heterostructures with superior hot-carrier transfer dynamics for plasmonics and optoelectronics

A Flexible Broadband Visible Light Plasmon‐Absorber Based on a 2D Monolayer of Au‐Nanoparticle/TiO2‐Nanowire Core–Shell Heterostructures

AbstractPlasmon‐induced hot carrier transfer is a promising approach for photoelectric applications, but its practical application is often hindered by its relatively narrow absorption bandwidth and low light harvesting at visible wavelengths. This work reports a broadband visible light plasmon‐absorber based on a dandelion‐like hierarchical metal‐semiconductor Au‐TiO2 core–shell nanostructure where each Au nanoparticle (AuNP) core is covered by an optically transparent mesh‐shell composed of TiO2 nanowires (TNWs) (denoted as AuTNW‐dCS). These AuTNW‐dCSs are assembled to form a 2D arrayed plasmonic monolayer by connecting adjacent AuNPs with cross‐linked TiO2 NWs, which can induce a remarkable broadband absorption in the visible spectrum of 500–700 nm. Driven by a wide light adsorption range, improved hot‐electron carriers, and excellent analyst's immobilization capability, the AuTNW‐dCS based photoelectric immunosensor owns excellent performance for alpha‐fetoprotein detection in human serum, with a practical linear range of 0.1–1000 ng mL−1, a low detection limit of 0.1 ng mL−1, and satisfying selectivity under visible light‐emitting diode light irradiation. This work enlightens the prospective research on the use of metal/semiconductor core–shell heterostructures as photoactive materials for sensing applications. Additionally, it gives an impetus for developing flexible nanofilms based on plasmonic metal/semiconductor nanohybrids, beneficial for building wearable point‐of‐need platform.

A Chemist's View on Electronic and Steric Effects of Surface Ligands on Plasmonic Metal Nanostructures.

ConspectusPlasmonic metal nanostructures have been extensively developed over the past few decades because of their ability to confine light within the surfaces and manipulate strong light-matter interactions. The light energy stored by plasmonic nanomaterials in the form of surface plasmons can be utilized to initiate chemical reactions, so-called plasmon-induced catalysis, which stresses the importance of understanding the surface chemistry of the plasmonic materials. Nevertheless, only physical interpretation of plasmonic behaviors has been a dominant theme, largely excluding chemical intuitions that facilitate understanding of plasmonic systems from molecular perspectives. To overcome and address the lack of this complementary understanding based on molecular viewpoints, in this Account we provide a new concept encompassing the well-developed physics of plasmonics and the corresponding surface chemistry while reviewing and discussing related references. Inspired by Roald Hoffmann's descriptions of solid-state surfaces based on the molecular orbital picture, we treat molecular interfaces of plasmonic metal nanostructures as a series of metal-ligand complexes. Accordingly, the effects of the surface ligands can be described by bisecting them into electronic and steric contributions to the systems. By exploration of the quality of orbital overlaps and the symmetry of the plasmonic systems, electronic effects of surface ligands on localized surface plasmon resonances (LSPRs), surface diffusion rates, and hot-carrier transfer mechanisms are investigated. Specifically, the propensity of ligands to donate electrons in a σ-bonding manner can change the LSPR by shifting the density of states near the Fermi level, whereas other types of ligands donating or accepting electrons in a π-bonding manner modulate surface diffusion rates by affecting the metal-metal bond strength. In addition, the formation of metal-ligand bonds facilitates direct hot-carrier transfer by forming a sort of molecular orbital between a plasmonic structure and ligands. Furthermore, effects of steric environments are discussed in terms of ligand-ligand and ligand-surface nonbonding interactions. The steric hindrance allows for controlling the accessibility of the surrounding chemical species toward the metal surface by modulating the packing density of ligands and generating repulsive interactions with the surface atoms. This unconventional approach of considering the plasmonic system as a delocalized molecular entity could establish a basis for integrating chemical intuition with physical phenomena. Our chemist's outlook on a molecular interface of the plasmonic surface can provide insights and avenues for the design and development of more exquisite plasmonic catalysts with regio- and enantioselectivities as well as advanced sensors with unprecedented chemical controllability and specificity.

Tuning the ZnO/GaN heterojunction for atmospheric NO abatement

Photocatalysis was a green and sustainable strategy for environmental remediation as it could accelerate the degradation/oxidation of pollutants using the widely available solar energy as the driving force. The efficacy of photocatalysis could be improved by the formation of a heterojunction and microstructure optimization of the semiconducting catalysts to manipulate the transfer of hot charge carriers. The re-oxidation of a visible light photocatalyst, (Ga, Zn)(N, O) (ZGN), was used for the in-situ production of ZnO/GaN(O) heterojunction with different surface properties for efficient NO oxidation. Re-oxidation at different temperatures imparted the new state of the surface oxide of the substrate (ZGN) anion redistribution by the mode strain between the oxide and the nitride, leading to the transformation of material properties. The ZGN-550 (ZnO/GaN(O)) showed a significantly higher oxidation efficiency (90.2%) than the pristine ZGN (62.3%) under visible light insolation, because the nanoscale discrete ZnO over the oxynitride matrix promoted the separation of charge carriers and the formation of reactive radicals (•OH and •O2–). The ZGN-550 heterojunction obtained a high apparent quantum efficiency of about 6.64% at photons around 400 nm. ZnO/GaN(O) heterojunction has great potential for sustainable and efficient degradation of air pollutants.

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

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.