Steady-state Spectroscopy Research Articles

Effects of Cosolvent and Nonsolvating Solvent on the Structural Dynamics of Organic Electrolytes in Sodium-Ion Batteries.

In sodium-ion batteries (SIBs), the performance of a single solvent often does not meet actual requirements and a cosolvent or nonsolvating solvent is needed. However, the effect of these electrolyte additives on the solvation structure and dynamics of Na+ in SIBs is yet to be fully understood. Herein, electrolyte structural dynamics are examined for NaPF6 in dimethyl carbonate (DMC) with 1,1,2,2-tetrafluoro-2,2,2-trifluoroethoxy ethane (HFE) as the nonsolvating solvent or propylene carbonate (PC) as the cosolvent using steady-state and time-resolved infrared (IR) spectroscopies. Molecular dynamics simulations show that the solvation size of Na+ decreases with a loosened structure upon adding the nonsolvating solvent, whereas its first solvation shell becomes denser and the second one becomes softened with decreased participation of the PF6- anion upon adding the cosolvent. While a decreased participation of DMC in the solvation layer of Na+ is suggested by linear IR results, an increased structural inhomogeneity (and hence overall more dynamical fluctuations) is found for Na+-coordinated DMC upon adding both additives by two-dimensional (2D) IR spectroscopy where the carbonyl stretch is used as a probe. The Na+/DMC/PC complex is found to structurally evolve slower than both Na+/DMC and Na+/DMC/HFE complexes on the picosecond time scales by spectral diffusion dynamics extracted from 2D IR diagonal signals. Frontier orbital theory calculations also indicate that both solvent additives are beneficial to increasing the stability of PF6-. The results obtained in this work provide important insights into the roles played by the solvent additives in influencing the solvation structures and dynamics of Na+, which are critical for understanding the Na+ transfer mechanism in SIBs.

Polarity of Ordered Solvent Molecules in 9,9'-Bianthracene Single Crystals Selects between Singlet Fission or Symmetry-Breaking Charge Separation.

Singlet exciton fission (SF) and symmetry-breaking charge separation (SB-CS) are both photophysical processes that can occur between two organic chromophores and are both of interest to improve solar energy conversion. Here, we tuned the photophysics of a 9,9'-bianthracene (BA) single crystal between SF and SB-CS using solvent intercalation to change the electric field within the crystal. Crystals of BA were grown in o-xylene, chlorobenzene, o-dichlorobenzene, and benzonitrile, as well as solvent-free from a melt. The crystals were studied by X-ray diffraction, steady-state optical spectroscopy, and transient absorption microscopy to elucidate the role of the intercalated solvent molecules. The crystals with no solvent in the structure undergo fast SF (<2 ps), while the crystals with intercalated moderately polar solvents o-xylene, chlorobenzene, and o-dichlorobenzene show evidence of charge-transfer-mediated SF. Finally, the crystals containing highly polar benzonitrile undergo SB-CS instead of SF. These results demonstrate that controlling solvation of BA in the crystal structure can tune its photophysics between SF and SB-CS.

Steric and Distance Effect on Electron Transfer in Dibenzo-Fused BODIPY-Based Photoredox Catalysts.

π-Extended BODIPY compounds are a compelling class of fluorophores known for their red or near-infrared (NIR) emission and high quantum yields, which are crucial for applications in materials science, solar cells, and biomedical imaging. Our recent study shows that we can use a dibenzo-fused BODIPY as a singlet-driven red photoredox catalyst by installing a simple electron donor group. Despite their potential in these applications, knowledge of electron transfer reactions involving dibenzo-fused BODIPY is still scarce. This paper presents the synthesis and systematic photophysical investigations of donor-acceptor (D-A) and donor-bridge-acceptor (D-bridge-A) series of dibenzo-fused BODIPY with N,N'-diethylaniline fragments serving as an electron donor. We examined the effects of methyl substituents and bridge length on the rates of photoinduced electron transfer (PeT). Through steady-state and time-resolved optical spectroscopy, electrochemistry, and density functional theory calculations, we elucidated how these simple structural modifications controlled the PeT rates and examined their impacts on catalytic activities in atom transfer radical addition (ATRA) reactions. Our results support previous studies on the (D-A) design of red heavy atom-free photocatalysts.

Photoresponsive Luminescent Silica Nanoparticles as Additive for 3D Printing and Electrospinning.

In this study, we present the synthesis and a versatile way to incorporate photoresponsive organic luminophores into polymeric materials using mesoporous silica nanoparticles (MSNs). The encapsulated thioethers within the MSNs were employed in polyvinyl alcohol (PVA) films, resin-based stereolithography, and electrospinning. Due to light-induced cyclization to dibenzothiophenes (DBTs), mmOC12 loaded materials were used to inscribe images using UV light. The DBTs formed from mmOC12 (mmDBTA/B) exhibit a long phosphorescence afterglow, which was investigated by steady-state and time-resolved photoluminescence spectroscopy. In addition, scanning electron microscopy (SEM) imaging, including energy dispersive X-ray spectroscopy (EDX), revealed the well-dispersed and intact MSNs in the polymeric materials. This approach shows a general way to incorporate non-polar organic luminophores into polymeric materials while retaining their unique emission properties.

Distance-Dependent Symmetry-Breaking Charge Transfer in 9,10- Bis(phenylethynyl)anthracene Dimers.

To investigate the effect of the through-bond coupling strength on the symmetry-breaking charge separation (SB-CS) dynamics and mechanism, three 9,10-bis((4-hexylphenyl)ethynyl)anthracene dimers with varying distances, viz., a single-bond linked dimer (0-dimer), a phenylene linked dimer (1-dimer) and a para-biphenylene linked dimer (2-dimer), were synthesized and studied systematically using steady-state and transient spectroscopy. Steady-state absorption spectra revealed that the electronic coupling strength decreased gradually with the increase of the inter-chromophore distance, and the transition of S0→S1 includes the dark charge transfer (CT) excitation. fs-TA spectra demonstrated that SB-CS could be conducted in both weakly and highly polar solvents for 0-dimer, but the SB-CS dynamics has a significant difference. In weakly polar solvents, SB-CS only produces the partial CT (PCT) state, but it could generate the CT state via the PCT state in highly polar solvent. In comparison, SB-CS is only proceeded in highly polar solvents in 1-dimer and 2-dimer to produce the CT state directly. These results demonstrate that the SB-CS dynamics is strongly dependent on the inter-chromophore electronic coupling, and the relatively strong electronic coupling is crucial for the occurrence of SB-CS in weakly polar environment that is commonly presented in photoelectric devices.

Modulation of the Chirality and Dynamics of Self-Assembled Nanocellulose-Chiral C-Dot Film for Chiral Sensing Applications.

The detection and sensing of chirality using chiral biomaterials are growing areas of research in advanced bioelectronics. As a result, chiral-controlled biomaterials are crucial for advancing current technologies in chiral sensing applications within biosystems. A chiral carbon dot (C-dot) modulated self-assembled emissive cellulose nanocrystal (CNC) film is developed where the chirality of the CNC film can be tempered between left-handed and right-handed chirality after being doped with chiral L/D-C-dots in CNCs (C-dot-CNC film), transferring the chirality from C-dots to CNCs. The interaction between C-dots, CNCs, and carrier dynamics is investigated using a variety of steady-state and time-resolved PL spectroscopy techniques. The chiral C-dot enhanced the protonic conductivity across the CNC via the formation of hydrogen bonds with its surface functional groups and water molecules. Further, the chiral CNC-C-dots photoelectrodes demonstrate an excellent ability to distinguish between left-handed and right-handed small molecules. These findings on the underlying mechanism of spin selectivity between chiral CNC-C-dot and chiral ligand hold promise for the development of efficient chiral-sensing electronic devices.

Host-guest interaction of Nileblue with cyclodextrins: A spectroscopic and computational approach

This study focuses on encapsulating the biologically active compound Nileblue (NB) within α, β and γ-cyclodextrins (CDs). CDs are widely used by pharmaceutical companies for drug delivery applications. Various spectroscopic techniques including time-resolved, steady-state and UV-visible spectroscopy, were employed to determine the extent of NB encapsulation within the cavities of CDs. Fluorescence lifetime measurements confirmed the formation of ground-state complexes, indicating static quenching. The binding interaction between NB and β-CD was further investigated by calculating thermodynamic parameters. The mode of inclusion complex formation was elucidated using NMR data. DFT calculations were performed to support these findings, demonstrating that NB fits comfortably inside the β-CD cavity. The in vitro Brine Shrimp toxicity (BST) assay was used to evaluate the toxicity of NB and its inclusion complex. Our results suggest that NB can be safely encapsulated in β-CD for applications in living systems without compromising its beneficial properties.

Structural and Electronic Factors Controlling the Efficiency and Rate of Intersystem Crossing to the Triplet State in Thiophene Polycyclic Derivatives.

Thiophene polycyclic derivatives are widely used in organic light-emitting diodes, photovoltaics, and medicinal chemistry applications. Understanding the electronic and structural factors controlling their intersystem crossing rates is paramount for these applications to be successful. This study investigates the photophysical, electronic structure, and excited state dynamics of 1,2-benzodiphenylene sulfide, benzo[b]naphtho[1,2-d]thiophene, and benzo[b]naphtho[2,3-d]thiophene in polar aprotic and non-polar solvents. Steady-state absorption and emission spectroscopy, femtosecond transient absorption spectroscopy, and DFT and TD-DFT calculations are employed. Low fluorescence quantum yields of 1.2 to 2.7 % are measured in acetonitrile and cyclohexene, evidencing that the primary relaxation pathways in these thiophene derivatives are nonradiative. Linear interpolation of internal coordinates calculations predict that an S-C bond elongation reaction coordinate facilitates the efficient intersystem crossing to the T1 state. Excitation of 1,2-benzodiphenylene sulfide and benzo[b]naphtho[1,2-d]thiophene at 350 nm or benzo[b]naphtho[2,3-d]thiophene at 365 nm, populates the lowest-energy 1ππ* state, which relaxes to the 1ππ* minimum in tens of picoseconds or intersystem crosses to the triplet manifold in ca. 500 ps to 1.1 ns depending on the position at which the benzene rings are added. Excitation at 266 nm does not affect the intersystem crossing rates. Laser photodegradation experiments demonstrate that the thiophene polycyclic derivatives are highly photostable.

Dibenzoquinone Cyclopentadithiophene Diradicaloids Show Optical Transitions of Different Spin States and Anomalous Near‐Infrared Emission

AbstractWe have prepared a series of bis(semiquinone) compounds with dithiophene bridges of different length that evolve from closed‐shell (smaller compound) to full diradical (longer compound) for which the narrow singlet‐triplet energy gap allows the triplet population at 298 K. The medium size system has a variety of photonic properties with absorptions and emission in the optical near‐infrared region mediated by a unique case of anti‐Kasha emission. A whole set of optical absorption/emission and vibrational steady state spectroscopies as well as picosecond transient absorption spectroscopy, all complemented with spectroelectrochemistry and theoretical calculations, is presented.

Dibenzoquinone Cyclopentadithiophene Diradicaloids Show Optical Transitions of Different Spin States and Anomalous Near-Infrared Emission.

We have prepared a series of bis(semiquinone) compounds with dithiophene bridges of different length that evolve from closed-shell (smaller compound) to full diradical (longer compound) for which the narrow singlet-triplet energy gap allows the triplet population at 298 K. The medium size system has a variety of photonic properties with absorptions and emission in the optical near-infrared region mediated by a unique case of anti-Kasha emission. A whole set of optical absorption/emission and vibrational steady state spectroscopies as well as picosecond transient absorption spectroscopy, all complemented with spectroelectrochemistry and theoretical calculations, is presented.

Concentration-Dependent Nonradiative Decay Mechanisms in Fluorescence Self-Quenching: Insights from Azulene and 1,3-Dichloroazulene

A series of steady-state and time-resolved spectroscopies were performed on azulene (Az) and its 1,3-dihalogenated analogue, 1,3-dichloroazulene (DCAz). Understanding the intra/inter-molecular interactions in these types of systems is the key to unlocking the potential of these molecules and enabling their application in a range of future devices. Therefore, the concentration dependence of their self-quenched fluorescence intensities and of the reduced lifetimes of their second-excited singlet states were examined. A Stern-Volmer analysis was implemented based on these experiments, which resulted in DCAz exhibiting a higher bimolecular quenching constant, compared to Az, due to its shorter excited-state lifetime. The highly efficient self-quenching at room temperature was a result of a short-range energy transfer mechanism.

Harnessing Visible Light for CO2 Conversion: The Role of Highly Reduced Phosphomolybdate Crystals as Powerful Photocatalysts.

Heterogeneous photocatalysts, characterized by well-defined atomic structures and the capacity for rapid, directional electron transfer, are pivotal in the exploration and development of highly efficient systems for visible-light-driven diluted CO2 reduction. Herein, we constructed highly reduced phosphomolybdates crystalline materials 1-3 to help this process, with the formula of [Co2(C8N3H7)4][Co2(C8N3H7)4(H2O)2][Co(H7P4Mo6O31)2]·8H2O (1), [Ni2(C8N3H7)4(H2O)2][Ni2(C8N3H7)4][Ni(H2O)4][Ni(H6P4Mo6O31)2]·3H2O·2C2H5OH (2), and [Zn2(C8N3H7)2][Zn2(C8N3H7)4][Zn2(C8N3H7)2(H2O)2][Zn(H5P4Mo6O31)2] (3) [C8N3H7 = 2-(1H-pyrazol-3-yl)pyridine]. Specifically, catalyst 1 demonstrated a CO production rate of 3276.4 μmol g-1 h-1 in an environment with 20% CO2 concentration, and an impressively elevated rate of 10740.3 μmol g-1 h-1 in a pure CO2 atmosphere. Steady-state photoluminescence spectroscopy revealed that the directional migration of photoelectrons from the Ru complexes to the catalyst was instrumental in enhancing the catalytic activity. This study provides valuable insights into the rational operation of low-concentration CO2 conversion treatment and the design and synthesis of photocatalysts.

Triad photosensitizers based on iodo-aza-Bodipy and naphthalenediimides (NDI) with broadband absorption: Study of resonance energy transfer and electron transfer

Two organic photosensitizers based on resonance energy transfer (A-1 and A-2) are prepared. Naphthalenediimides was used as intramolecular energy donor and iodo-aza-Bodipy was used as intramolecular energy acceptor/spin converter. A-1 (ε = 42,800 at 618 nm and ε = 59,600 at 674 nm) and A-2 (ε = 33,300 at 514 nm and ε = 68,300 at 674 nm) give the two strong absorption band and both of them show broadband absorption in visible region. The photophysical properties of the compounds were studied with steady state and time-resolved spectroscopy in detail. With steady state and time-resolved spectroscopy, we found that photoexcitation into the energy donor was followed by singlet energy transfer, then via the intersystem crossing (ISC) of the energy acceptor. By nanosecond time-resolved transient absorption spectroscopy and DFT calculation, triplet excited state is localized on the iodo-aza-Bodipy moiety. Quantum yield of singlet oxygen of A-1 and A-2 is 39.7 % and 40.9 %, respectively. Based on fluorescence lifetime quenching, the efficiency of intramolecular energy transfer is estimated to be 15.9 % and 27.7 % for A-1 and A-2. And PET is responsible for the relatively low efficiency, which is identified by the calculation of kcs/kFRET and the Gibbs free energy change (△G0cs). A-1 and A-2 were used for singlet oxygen (1O2) mediated photooxidation of 1,5-dihydroxylnaphthalene and the photosensitizing ability are more efficient than the triplet photosensitizers with the mono-chromophore photosensitizer.

Controlled Photooxidation via Singlet Oxygen Generation by Triplet Harvesting in a Heavy Atom Free Pure Organic Dithienylethene-Naphthalene Diimide.

Noninvasive control over the reversible generation of singlet oxygen (1O2) has found the enormous practical implications in the field of biomedical science. However, metal-free pure organic emitters, connected with a photoswitch, capable of generating "on-demand" 1O2 via triplet harvesting remain exceedingly rare; therefore, the utilization of these organic materials for the reversible control of singlet oxygen production remains at its infancy. Herein, an ambient triplet mediated emission in quinoline-dithienylethene (DTE)-core-substituted naphthalene diimide (cNDI) derivative is unveiled via delayed fluorescence. The quinoline-DTE-cNDI triad displayed enhanced photoswitching efficiency via double FRET mechanism. It was found to have direct utilization in controlled photosensitized organic transformations via efficient generation of singlet oxygen (yield ΦΔ~0.55 in DCM and 0.73 in methanol). The designed molecule exhibits a long-lived emission (τ∼1.1 μs) and very small singlet-triplet splitting (ΔEST) of 0.13 eV empowering it to display delayed fluorescence. Comprehensive steady state and time-resolved emission spectroscopy (TRES) analyses along with DFT calculations offer detailed understandings into the excited-state manifolds of organic compound and energy transfer (ET) pathways involved in 1O2 generation.

Solvent polarity-driven modulation of excited states: A DFT and spectroscopic analysis

The relationship between the photophysical properties of N,N,N’,N’-tetra-p-tolyl-benzidine (TTB) and [1,4-bis[2-[4-[N,N-di(p-tolyl)amino]phenyl]vinyl]benzene (DSB) molecules and solvent polarity was explored through steady-state spectroscopy, femtosecond transient absorption spectroscopy, and quantum chemical calculations. Computational results and steady-state spectra reveal that the lowest singlet excited states of TTB and DSB are primarily characterized by localized excited (LE) states in nonpolar cyclohexane (CHX), whereas intramolecular charge transfer (ICT) components predominate in highly polar acetonitrile (ACN). Compared to TTB, the excited-state potential of DSB demonstrates a heightened sensitivity to solvent polarity, exhibiting larger dipole moments due to enhanced electron transfer enabled by the incorporation of styrene groups. Ultrafast femtosecond transient absorption spectroscopy distinctly shows the transition from LE states in nonpolar CHX to ICT states in highly polar ACN. The deactivation mechanisms were further elucidated to understand how solvent polarity modulates excited states and high quantum yields, providing valuable insights for the design and application of photophysical materials.

On the glow of cremated remains: long-lived green photo-luminescence of heat-treated human bones.

The long-lived green luminescence of human bone (that has been heated to 600°C for a short duration) is attributed to a carbon quantum dot material (derived from collagen) encapsulated and protected by an inorganic matrix (derived from bone apatite) and is more intense in dense rigid and crystalline parts of (healthy) human bones. The strong collagen-apatite interaction results (upon decomposition) in a protective inorganic environment of the luminescent centers allowing long-lived triplet-based emission of a carbon (quantum) dot-like material at room temperature, as well as resilience against oxidation between 550 and 650°C. The graphitic black phase (obtained upon heating around 400°C) is a precursor to the luminescent carbon-based material, that is strongly interacting with the crystalline inorganic matrix. Human bone samples that have been heated to 600°C were subjected to steady-state and time-resolved spectroscopy. Excitation-emission matrix (EEM) luminescence spectroscopy revealed a broad range of excitation and emission wavelengths, indicating a heterogeneous system with a broad density of emissive states. The effect of low temperature on the heat-treated bone was studied with Cryogenic Steady State Luminescence Spectroscopy. Cooling the bone to 80K leads to a slight increase in total emission intensity as well as an intensity increase towards to red part of the spectrum, incompatible with a defect state model displaying luminescent charge recombination in the inorganic matrix. Time-resolved spectroscopy with an Optical Multichannel Analyzer (OMA) and Time Correlated Single Photon Counting (TCSPC) of these samples showed that the decay could be fitted with a multi-exponential decay model as well as with second-order decay kinetics. Confocal Microscopy revealed distinct (plywood type) structures in the bone and high intensity-fast decay areas as well as a spatially heterogeneous distribution of green and (fewer) red emissive species. The use of the ATTO 565 dye aided in bone-structure visualization by chemical adsorption. Conceptually our data interpretation corresponds to previous reports from the material science field on luminescent powders.

Excited State Bond Homolysis of Vanadium(V) Photocatalysts for Alkoxy Radical Generation.

Advancements in photocatalysis have transformed synthetic organic chemistry, using light as a powerful tool to drive selective chemical transformations. Recent approaches have focused on metal-halide ligand-to-metal charge transfer (LMCT) photoactivated bond homolysis reactions leveraged by earth-abundant elements to generate valuable synthons for radical-mediated cross-coupling reactions. Of recent utility, oxovanadium(V) LMCT photocatalysts exhibit selective alkoxy radical generation from aliphatic alcohols upon blue light (UVA) irradiation under mild conditions. The selective photochemical liberation of alkoxy radicals is valuable for applying late-stage fragmentation approaches in organic synthesis and depolymerization strategies for nonbiodegradable polymers. Steady-state and time-resolved spectroscopy were used to assign the electronic structure of three well-defined V(V) photocatalysts in their ground and excited states. We assign the excited state for this transformation at earth-abundant vanadium(V), interrogating the electronic structure using static UV-visible absorption, ultrafast transient absorption, and electron paramagnetic resonance spectroscopy coupled to computational approaches. These findings afford assignments of the short-lived excited state intermediates that dictate selective homolytic bond cleavage in metal alkoxides, illustrating the valuable insight gleaned from fundamental investigations of the molecular photochemistry responsible for light-escalated chemical transformations.

Overcoming Microstructural Defects at the Buried Interface of Formamidinium-Based Perovskite Solar Cells.

Since the advent of formamidinium (FA)-based perovskite photovoltaics (PVs), significant performance enhancements have been achieved. However, a critical challenge persists: the propensity for void formation in the perovskite film at the buried perovskite-interlayer interface has a deleterious effect on device performance. With most emerging perovskite PVs adopting the p-i-n architecture, the specific challenge lies at the perovskite-hole transport layer (HTL) interface, with previous strategies to overcome this limitation being limited to specific perovskite-HTL combinations; thus, the lack of universal approaches represents a bottleneck. Here, we present a novel strategy that overcomes the formation of such voids (microstructural defects) through a film treatment with methylammonium chloride (MACl). Specifically, our work introduces MACl via a sequential deposition method, having a profound impact on the microstructural defect density at the critical buried interface. Our technique is independent of both the HTL and the perovskite film thickness, highlighting the universal nature of this approach. By employing device photoluminescence measurements and conductive atomic force microscopy, we reveal that when present, such voids impede charge extraction, thereby diminishing device short-circuit current. Through comprehensive steady-state and transient photoluminescence spectroscopy analysis, we demonstrate that by implementing our MACl treatment to remedy these voids, devices with reduced defect states, suppressed nonradiative recombination, and extended carrier lifetimes of up to 2.3 μs can be prepared. Furthermore, our novel treatment reduces the stringent constraints around antisolvent choice and dripping time, significantly extending the processing window for the perovskite absorber layer and offering significantly greater flexibility for device fabrication.

Pressure-Induced Changes in the Phase Distribution and Carrier Dynamics of Quasi-Two-Dimensional Ruddlesden-Popper Perovskites.

Quasi-two-dimensional (quasi-2D) perovskites hold significant potential for diverse design strategies due to their tunable structures, exceptional optical properties, and environmental stability. Due to the complexity of the structure and carrier dynamics, characterization methods such as photoluminescence and absorption spectroscopy can observe but cannot precisely distinguish or identify the phase distribution within quasi-2D perovskite films or correlate phases with carrier dynamics. In this study, we used pressure to modulate the intralayer and interlayer structures of (PEA)2Csn-1PbnBr3n+1 quasi-2D perovskite films, investigating charge carrier dynamics. Steady-state spectroscopy revealed phase transitions at 1.62, 3, and 8 GPa, with free excitons transforming into self-trapped excitons after 8 GPa. Transient absorption spectroscopy elucidated the structural evolution, energy transfer, and pressure-induced transition mechanisms. The results demonstrate that combining pressure and spectroscopy enables the precise identification of phase distribution and pressure response ranges and reveals photophysical mechanisms, providing new insights for optimizing optoelectronic materials.

Promoting photoelectric performance through extraction of hot electron from Cu-doped CdSe quantum dots

Efficient extraction of photogenerated hot carriers and insight into the involved dynamics are crucial to promoting the photoelectric efficiencies of photovoltaic and photocatalytic devices. Here, we synthesized Cu-doped CdSe quantum dots (Cu-CdSe QDs) as the donor and investigated the ultrafast dynamics of hot electron cooling and electron transfer from Cu-CdSe QDs to benzoquinone (BQ) as the acceptor. The doping of copper ion effectively suppresses the cooling rate of hot electrons in CdSe QDs and extends the lifetime of hot electrons from 0.2 ps to 3.6 ps. The results of steady-state and time-resolved spectroscopy demonstrate that the overall electron transfer efficiency from Cu-CdSe QDs to BQ exceeds 70 %. Dynamical analysis confirms that two electron transfer pathways of hot and band-edge electrons exist in the Cu-CdSe-BQ composites. The hot electron transfer efficiency can reach ∼45 % with a rate constant of 3.90 × 1011 s−1. The band-edge electron transfer efficiency is about 50 %. These findings demonstrate an effective strategy for improving the photoelectric performance of Cu-CdSe-BQ composites by efficiently separating photogenerated carriers and extracting hot electrons.