Rapid Electron Injection Research Articles

Sustainable Carbon Dioxide Reduction of the P3HT Polymer-Sensitized TiO2/Re(I) Photocatalyst.

In this study, a p-type π-conjugated polymer chain, poly(3-hexylthiophene-2,5-diyl) (P3HT), was physically adsorbed onto n-type TiO2 nanoparticles functionalized with a molecular CO2 reduction catalyst, (4,4-Y2-bpy)ReI(CO)3Cl (ReP, Y = CH2PO(OH)2), to generate a new type of P3HT-heterogenized hybrid system (P3HT/TiO2/ReP), and its photosensitizing properties were assessed in a heteroternary system for photochemical CO2 reduction. We found that P3HT immobilization on TiO2 facilitated photoinduced electron transfer (PET) from photoactivated P3HT* to the n-type TiO2 semiconductor via rapid interfacial electron injection (∼65 ps) at the P3HT and TiO2 surface interface (P3HT* → TiO2). With such effective charge separation, the heterogenization of P3HT onto TiO2 resulted in a steady electron supply toward the co-adsorbed Re(I) catalyst, attaining durable catalytic activity with a turnover number (TON) of ∼5300 over an extended time period of 655 h over five consecutive photoreactions, without deformation of the adsorbed P3HT polymer. The long-period structural stability of TiO2-adsorbed P3HT was verified based on a comparative analysis of its photophysical properties before and after 655 h of photolysis. To our knowledge, this conversion activity is the highest reported so far for polymer-sensitized photochemical CO2 reduction systems. This investigation provides insights and design guidelines for photocatalytic systems that utilize organic photoactive polymers as photosensitizing units.

InP-Quantum Dot Surface-Modified TiO2 Catalysts for Sustainable Photochemical Carbon Dioxide Reduction

In this study, an InP-cored quantum dot (InP-QD) material was prepared and physically immobilized on TiO2 particles functionalized with an archetypical reduction catalyst, (4,4-Y2-bpy)ReI(CO)3Cl (ReP, Y = CH2PO(OH)2), to form a new type of InP quantum dot-sensitized hybrid photocatalyst (InP-QD/TiO2/ReP) and evaluated as a lower-energy photosensitizer in this hybrid system. It was found that the TiO2 heterogenization of the InP-QD material promotes the photoexcited electron transfer process from the photoexcited InP-QD* to the inorganic TiO2 solid with rapid electron injection (by ∼25 ps) through oxidative quenching, resulting in efficient charge separation at the InP-QD/TiO2 interface. With such an effective photosensitization, the stabilization of the structurally vulnerable InP-cored QDs by TiO2 heterogenization resulted in highly efficient and durable photochemical CO2-to-CO conversion of the InP-QD/TiO2/ReP hybrid in a 10 times-repeated photolysis, giving a turnover number of ∼51,000 over a 420 h period without any damage to the InP-QD photosensitizer. The stability of TiO2-bound InP-QDs was confirmed by the comparative analysis of their photophysical and chemical structures before and after long-term photoreaction. This catalytic performance is the highest reported for QD-sensitized photocatalytic CO2 conversion systems using sacrificial organic electron donors. This study provides useful design guidelines for photocatalysts using QD materials as photosensitizing components.

Photocatalytic activity of hybrid P450 Enzymes

The Cytochromes P450 are heme-thiolate enzymes that carry out selective oxyfunctionalization of a wide range of substrates using molecular dioxygen and two reducing equivalents provided by redox partner enzymes. Alternative approaches to activate P450 enzymes have received recent attention in an attempt to circumvent the use of redox partners and cofactors. In particular, the use of light-harvesting units has proven useful in triggering P450 activity upon visible light-excitation. Our laboratory has taken advantage of the inorganic Ru(II)-diimine photosensitizers and their unique excited properties to harness P450 synthetic potential. Their covalent attachment to non-native single cysteine residues has enabled rapid electron injection into the heme domain of several P450 enzymes leading to high photocatalytic activity and coupling efficiency. Recently, we also developed a bimolecular system to activate P450 with peroxygenase activity. The crystal structure of the most efficient hybrid enzyme reveals that the photosensitizer is ideally positioned to deliver electrons to the heme active site utilizing the natural electron transfer pathway. A combination of rational and directed evolution approaches are currently employed to optimize the biocatalyst photocatalytic activity and expand the scope of the light-driven P450 activity. In addition, the tunability and derivatization of the inorganic complexes have promoted the formation of dimeric structures and heterogeneous biocatalysts and provided insights into the rate-limiting steps in the light-driven hybrid P450 enzyme.

The Laser-Induced Potential Jump: A Method for Rapid Electron Injection into Oxidoreductase Enzymes.

Oxidoreductase enzymes often perform technologically useful chemical transformations using abundant metal cofactors with high efficiency under ambient conditions. The understanding of the catalytic mechanism of these enzymes is, however, highly dependent on the availability of well-characterized and optimized time-resolved analytical techniques. We have developed an approach for rapidly injecting electrons into a catalytic system using a photoactivated nanomaterial in combination with a range of redox mediators to produce a potential jump in solution, which then initiates turnover via electron transfer (ET) to the catalyst. The ET events at the nanomaterial-mediator-catalyst interfaces are, however, highly sensitive to the experimental conditions such as photon flux, relative concentrations of system components, and pH. Here, we present a systematic optimization of these experimental parameters for a specific catalytic system, namely, [FeFe] hydrogenase from Chlamydomonas reinhardtii (CrHydA1). The developed strategies can, however, be applied in the study of a wide variety of oxidoreductase enzymes. Our potential jump system consists of CdSe/CdS core-shell nanorods as a photosensitizer and a series of substituted bipyridinium salts as mediators with redox potentials in the range from -550 to -670 mV (vs SHE). With these components, we screened the effect of pH, mediator concentration, protein concentration, photosensitizer concentration, and photon flux on steady-state photoreduction and hydrogen production as well as ET and potential jump efficiency. By manipulating these experimental conditions, we show the potential of simple modifications to improve the tunability of the potential jump for application to study oxidoreductases.

Dual function of graphene oxide for assisted exfoliation of black phosphorus and electron shuttle in promoting visible and near-infrared photocatalytic H2 evolution

The search for suitable photocatalysts with broadband absorption in visible and near-infrared (NIR) region is recognized as one of the most challenging issues on solar energy utilization. Black phosphorous (BP) is demonstrated as an effective visible and NIR activated material in solar energy conversion. However, traditional liquid exfoliation yield is low and the rigid structure and insoluble properties of pristine BP hinder its high-yield of hybridization. Herein, a new and stable noble-metal-free ternary photocatalyst molybdenum disulfide (MoS2)-BP/graphene oxide (GO) was constructed for splitting water to H2, showing dual functions of GO in synthetic and photocatalytic processes. Under visible-NIR light irradiation, the H2 evolution rates of MoS2-BP/GO was enhanced to 3.47 μmol h−1. Rapid electron injection efficiency from excited BP to GO and to MoS2 was confirmed by femtosecond transient absorption spectroscopy. This study provides new insight into the design of nanomaterials, and offers a noble-metal-free protocol with photocatalytic H2 production.

Template free synthesis of CdSnO3 micro-cuboids for dye sensitized solar cells

Mesoporous transparent conducting oxide, CdSnO3 has been synthesized using ultrasonication assisted co-precipitation method. Rather employing any template or structure directing agent, the co-precipitation effect of sodium hydroxide and citric acid were able to form cuboid shaped CdSnO3 during the sonochemical treatment as investigated by a systematic X-ray diffraction and field emission scanning electron microscopy studies. An optimum 3:1 molar concentration of NaOH and citric acid leads to form cuboidal structure of CdSnO3 on calcined at 700 °C. Further calcination at 800 °C converted cuboids to nanoparticles. Comparative studies have been carried out between the cuboid and particle morphology to understand the physico-chemical properties related to the morphology using various characterization techniques. Further, the CTO cuboids and the decomposed nanoparticles have been tested as photoanode for dye sensitized solar cell applications. The cuboid based photoanode exhibited an enhanced efficiency of 3.23% with a VOC of 0.72 V than its decomposed nanoparticle which exhibited a lower efficiency of 2.67%. The electrochemical impedance and incident photon to electron conversion efficiency results also support enhanced performance of cuboid based device than particle. The overall results show the advantage of cuboidal CdSnO3 in rapid electron injection and higher light reflection leading to improved current density of the DSSC device than the decomposed nanoparticle form. The results establish the application of less explored CdSnO3 as a photoanode in DSSCs application.

Non-toxic configuration of indium selenide nanoparticles- Cu2ZnSnS2Se2 /carbon fabric in a quasi solid-state solar cell

Non-toxic indium selenide (In2Se3) semiconducting nanoparticles as photosensitizers and an alloyed copper-zinc-tin-sulfide-selenide (Cu2ZnSnS2Se2) coated carbon-fabric as counter electrode are assembled into a solar cell configuration for the first time. In2Se3 nanoparticles with a band gap of 1.78 eV, harvest blue-green photons as well as some portion of the red region of the solar spectrum and they exhibit a broad emission in the visible region, and the emissions via absorption of high energy- and low energy-photons show short and long excited electron lifetimes respectively. A polymeric electrolyte with poly(hydroxyethyl methacrylate) as the gelatinizing agent is employed as the hole transport layer in solar cells. Cu2ZnSnS2Se2/carbon-fabric is more efficient than carbon-fabric as a counter electrode, for the solar cell based on the former shows a lower electron transport resistance, a higher recombination resistance at the photoanode/gel interface, and an increased chemical capacitance for the photoanode, cumulatively resulting in rapid electron injection to the electrolyte at the cathode. The champion solar cell with TiO2/In2Se3-S2-/poly(hydroxyethyl methacrylate) gel-Cu2ZnSnS2Se2/carbon-fabric architecture delivers a power conversion efficiency of 4.15%, thus demonstrating that quasi solid-state quantum dot solar cells with non-toxic components can be easily fabricated and even scaled up for real time applications.

Synthesis and Photophysical Properties of a Covalently Linked Porphyrin Chromophore–Ru(II) Water Oxidation Catalyst Assembly on SnO2 Electrodes

We describe here the preparation and surface photophysical properties of a covalently linked, chromophore-catalyst assembly between a phenyl phosphonate-derivatized pentafluorophenyl-substituted porphyrin and the water oxidation catalyst, [RuII(terpyridine)(2-benzimidazolylpyridine)(OH2)]2+, in a derivatized assembly of porph-RuII–OH22+. The results of nanosecond transient absorption measurements on nanoparticle SnO2 electrodes in aqueous acetate buffer at pH 4.7 are consistent with rapid electron injection into SnO2 with transfer of oxidative equivalents to the assembly. Electron transfer from the singlet excited state of the porphyrin to the conduction band of the electrode, SnO2(e–)|-porph+-RuII–OH22+, is favored as the porphyrin singlet excited state lies 0.44 eV above the SnO2 conduction band edge. Electron injection is rapid (⟨τinj⟩ < 10–8 s), and occurs with high efficiency. Based on measured redox potentials, following excitation and injection, intra-assembly oxidation of the catalyst, -porph+-RuII–OH22+ → -porph-RuIII–OH2+ + H+, is favored in the transient equilibrium state by 0.62 eV at pH 4.7. However, immediately after the flash, a distribution exists at the surface between isomers with SnO2(e–)|-porph+-RuII–OH22+ undergoing back electron transfer to the surface with an average lifetime of ⟨τ1⟩ ∼ 10–7 s and a slower component for back electron transfer from SnO2(e–)|-porph-RuIII–OH2+ with ⟨τ2⟩ ∼ 4 × 10–5 s.

Direct Z-scheme g-C3N4/WO3 photocatalyst with atomically defined junction for H2 production

Mimicking the natural photosynthesis, artificial Z-scheme photocatalysis enables more efficient utilization of solar energy for sustainable chemical fuel production. Herein, a direct Z-scheme g-C3N4/WO3 photocatalyst with host-guest architecture is rationally designed, demonstrating significantly enhanced activities of photocatalytic H2 production. Unprecedented atomic-scale imaging of both the in-plane and interlayer structures in g-C3N4 revealed the well-defined interfaces in such architecture, where the 2D g-C3N4 layers stand vertically on the flat facets of WO3 nanocuboids. Through both experimental and theoretical investigations, mechanistic insights regarding the direct Z-scheme electron transfer from WO3 to g-C3N4 were obtained. The Z-scheme electron transfer was driven by the internal electric field at the interfacial junction, defined by the covalent W-O-N-(C)2 interaction. Under simultaneous light excitation, this atomically defined junction induces a rapid electron injection from WO3 to inhibit the fast recombination kinetics within g-C3N4 and prolong the charge carrier lifetime of g-C3N4, thereby liberating more excited electrons with high reducing power for H2 production.

A theoretical study of structural, opto-electronic and nonlinear properties of arylboroxine derivatives

Density functional theory at CAM-B3LYP/6-311G++ (2d, 2p) level was employed to study the Triphenylboroxine derivatives (TB) containing electron donating and electron substituents, for their charge transfer and nonlinear optical properties. The results reveal that electron donating groups facilitate the rapid electron injection as compared to unsubstituted TB. It was observed that upon substitution with electron donating groups, the TB derivatives show an increased double bond character in the B3–C18 bond indicating an increase in the degree of conjugation. The Frontier molecular orbital studies indicate that highest occupied molecular orbitals of the neutral molecules delocalize primarily over the three phenyl rings and bridging oxygen atoms, whereas the lowest unoccupied molecular orbitals localize largely on the two phenyl rings and the boron atoms. Further, the TD-DFT studies indicate that the maximum absorption band results from the electron transitions from the initial states that are contributed by the HOMO and HOMO-1 to the final states that are mainly contributed by the LUMOs. In addition, we have observed that the introduction of electron donating group to the TB-7 leads to more active nonlinear performance.

Photoinduced Triplet State Electron Transfer Processes From Ruthenium Containing Triblock Copolymers To Carbon Nanotubes

A light-harvesting triblock copolymer incorporated with pyrene and ruthenium complex photosensitizing moieties was synthesized and integrated into the dispersion and surface functionalization of multiwalled carbon nanotubes (MWCNTs) via noncovalent π–π interactions. Molecular dynamics simulation results show that the copolymer interacts with MWCNTs mainly through the pyrene blocks and that the Ru complex moieties far away from the MWCNT could preserve the charge-separated states of the electron donor–acceptor system after photo excitation. This new molecular structure serves as a good model for studying the fundamental photophysics of light harvesting systems based on polymer/carbon nanotube hybrids. Results from femtosecond transient absorption spectroscopy show that the electron transfer process occurs within 383 ps from the Ru complex to MWCNT, which is much faster than the relaxation of the triplet metal-to-ligand charge transfer excited state of the Ru complex. The rapid electron injection process in...

Fabrication of graphene-modified nano-sized red phosphorus for enhanced photocatalytic performance

In this present paper, nano-sized red phosphorus particles (NRP) were prepared through a mechanical milling and ultrasonic flotation method. The as-prepared red phosphorus nano particles were loaded on the surface of graphene. The residual oxidative bonds on the surfaces of the red phosphorus and graphene were carried out to form effective interface contact. The present results indicated that comparing with large size commercial red phosphorus particles, NRP possesses higher specific surface area and photocatalytic activity. The NRP/graphene composite shows a great adsorption capacity for rhodamine (RhB). Meanwhile, its visible-light-driven decolorization performance for RhB was 5 times higher than that of pure NRP, which can decolorize of RhB completely in only 3min. So, NRP/graphene composite photocatalyst possess great potential in the area of environment organic pollution purge. Electrochemical impedance spectra (EIS) and Mott-Schottky spectra results of these samples indicated that a downward bend of the conduction band of NRP was formed when it contacted with graphene, resulting in a rapid electron injection into the graphene. Therefore, the probability of recombination of photogenerated carriers was inhibited effectively, thus enhanced the overall photocatalytic performance of the composite material.

Perovskite solar cells based on bottom-fused TiO2nanocones

Compared to the fast electron transport in perovskite and rapid electron injection from perovskite to TiO2nanoparticle scaffold, the slower electron transport rate in mesoporous TiO2is reported to be a hindrance factor for power conversion efficiency.

Rapid Electron Injection in Nitrogen- and Fluorine-Doped Flower-Like Anatase TiO2 with {001} Dominated Facets and Dye-Sensitized Solar Cells with a 52% Increase in Photocurrent

Nitrogen- and fluorine-doped flower-like anatase TiO2 (NF-TiO2) with {001} dominated facets was fabricated by a facile hydrothermal method. We investigated its electrical and optical properties, applied it in dye-sensitized solar cells as an electrode material, and achieved an improved conversion efficiency of 8.20%. There was a 52% increase in the photocurrent and 22% improvement in the conversion efficiency. Such improvements mainly arise from the positive-shift flat band, increasing the driving force of electrons and then improving the electron injection efficiency from the lowest unoccupied molecular orbital (LUMO) of the dye and the conduction band of TiO2; from the incorporation of the flower-like anatase NF-TiO2 crystals with exposed {001} facets, serving as effective light-scattering centers and improving the reactivity, both important attributes for achieving a higher light harvesting and thus an improved Jsc and conversion efficiency; and from the narrowed band gap, expanding the response in the...

High Extinction Coefficient Ru‐Sensitizers that Promote Hole Transfer on Nanocrystalline TiO2

Two series of Ru(II) polypyridyl compounds with formulas [(bpy)2RuL](PF6)2 and [(deeb)2RuL](PF6)2, where bpy is 2,2'-bipyridine, deeb is 4,4'-diethylester-2,2'-bpy, and L is one of several substituted 9'-(1,3-dithiole-2-ylidene)-4',5'-diazafluorene ligands, were studied as potential photosensitizers for TiO2. These compounds possess notably high extinction coefficients (≥40,000 M(-1) cm(-1) @470 nm) which are shown by time-dependent density functional theory (TD-DFT) calculations to result from overlapping metal-to-ligand charge transfer (MLCT) and ligand-localized transitions. Low-temperature absorption and photoluminescence measurements were suggestive of a short-lived MLCT excited state. When adsorbed onto TiO2 thin films, both the free ligands (L) and their corresponding [(deeb)2RuL](2+) complexes exhibited rapid excited-state electron injection into TiO2; in the case of the complexes, this was followed by rapid (k>10(8) s(-1)) hole transfer from Ru(III) to the 1,3-dithiole ring of the L ligand. Observation of diffusion-limited reductive quenching of the [Ru(bpz)3](2+)* (bpz is 2,2'-bipyrazine) excited state by the L ligands in solution supported the occurrence of intramolecular hole transfer following electron injection by the TiO2-anchored complexes.

Au@poly(acrylic acid) plasmons and C60 improve the light harvesting capability of a TiO2/CdS/CdSeS photoanode

A quantum dot solar cell (QDSC) was developed using a photoanode with CdS and CdSeS QDs as co-sensitizers, fullerene (C60) clusters as electron conduits and Au nanoparticles capped by poly(acrylic acid) or Au@PAA as plasmons, which were all tethered to TiO2 as the semiconducting scaffold. The formation of CdSeS QDs and hexagon-shaped Au@PAA, each with a face-centered cubic lattice, was confirmed by high-resolution transmission electron microscopy. Evidence for rapid electron injection from CdS or CdSeS to C60 and Au@PAA, as well as for inter-dot electron transfer from CdS to CdSeS, were obtained from fluorescence quenching and emission decay lifetime analyses. The fastest electron deactivation pathway was achieved in the TiO2/CdS/CdSeS/C60/Au@PAA electrode, which demonstrated the ability of C60 and Au@PAA to serve as efficient electron sinks due to their high electronic conductivities and their favorably poised Fermi levels. Au@PAA particles induced absorbance increments of CdS and CdSeS QDs, thus indicating that plasmonic improvements could be exploited in the photoanode using the same. High electron transfer rates and plasmonic effects translated into a high overall power conversion efficiency of 3.61% for a QDSC constructed with this composite as the photoanode, aqueous S2− as the electrolyte and carbon-nanotube-based counter electrode. The efficiencies of cells without Au@PAA and C60 were lower by ∼19% and 23%, respectively, confirming the synergy between C60 and Au@PAA in producing larger photocurrents. Aligned conduction bands in the TiO2/CdS/CdSeS/C60/Au@PAA electrode that permitted electron transfer by cascade, broader spectral utilization by using CdS and CdSeS and near field plasmonic enhancement by Au@PAA due to its proximity with the QDs, cumulatively manifested in an incident photon to current conversion efficiency of 48%, which is 25% greater than that of the cell without Au@PAA. Our study shows that significant improvements in QDSC performances can be realized by simply developing more efficient designs for photoanode configurations.

Watching Photoactivation in a Ru(II) Chromophore–Catalyst Assembly on TiO2 by Ultrafast Spectroscopy

This paper examines the ultrafast dynamics of the initial photoactivation step in a molecular assembly consisting of a chromophore (denoted [RuaII]2+) and a water-splitting catalyst (denoted [RubII]2+) anchored to TiO2. Photoexcitation of the chromophore is followed by rapid electron injection from the Ru(II) metal-to-ligand charge-transfer (MLCT) excited state. The injection process was followed via the decay of the bpy radical anion absorption at 375 nm. Injection is ∼95% efficient and exhibits multiple kinetic components with decay times ranging from <250 fs to 250 ps. Electron injection is followed by the transfer of the oxidative equivalent from the chromophore to the catalyst (ΔG = −0.28 eV) with a transfer time of 145 ps. In the absence of subsequent photoexcitation events, the charge-separated state undergoes electron-transfer recombination on the microsecond time scale.

The effect of ruthenium on the performance of porphyrin dye and porphyrin–fullerene dyad solar cells predicted by DFT and TD-DFT calculations

The effect of ruthenium on the performance of porphyrin dye and porphyrin–fullerene (PF) dyad solar cells is investigated by using density functional theory and time-dependant density functional theory calculations. The results reveal that ruthenium facilitates rapid electron injection from porphyrin to fullerene, narrows the band gaps of porphyrin dye and PF dyad and alters the density of states near the corresponding Fermi levels. The HOMOs are localised on the donor moieties and the LUMOs on the acceptor moieties. The donor and acceptor dyads form good donor–acceptor pairs for photo-to-current conversion under the effect of ruthenium. HOMOs of porphyrin and ruthenium metalloporphyrin dyes fall within the (TiO2)60 and Ti38O76 gaps, and support the issue of typical interfacial electron transfer reaction. The calculated transition energies of porphyrin are almost insensitive to ethanol solvent effects. The introduction of ruthenium to the porphyrin ring leads to more active nonlinear optical performance, stronger response to the external electric field and induces higher photo-to-current conversion efficiency. Moreover, ruthenium shifts the absorption bands of porphyrin and makes it a potential candidate for harvesting light for photovoltaic applications.

Screening of thiophene-substituted metalloporphyrins (Zn, Ni, Fe, Ti) for use in dye-sensitized solar cells DFT and TD-DFT study

We aim to optimize the performance of the title solar cells by altering the frontier orbital energy gaps. This was done by adding low-cost metal atoms (Zn, Ni, Fe, Ti) to the free-base porphyrin, and increasing the length and conjugation of the thiophene substituent. The results reveal that cell efficiency can be enhanced by metal functionalization of the free-base porphyrin, and increasing the π-conjugation and electron-withdrawing capability of the thiophene-substituted side chain. While Ti-porphyrin was found to be the most efficient dye sensitizer for dye-sensitized solar cells (DSSCs) based on metalloporphyrin donors and conjugated thiophene side chain acceptors, Fe-porphyrin was found to be the most efficient sensitizer for DSSCs based on metalloporphyrin donors and a series of oxide semiconductor acceptors. Metal atoms and thiophene side chains facilitate rapid electron injection from the donor moiety to the acceptor moiety, narrow the band gaps of the donors, acceptors, and donor–acceptor dyads, and alter the density of states near the Fermi levels. The highest occupied molecular orbitals (HOMOs) of the dyads are close to the HOMOs of the donors, and lowest unoccupied molecular orbitals (LUMOs) are close to the LUMOs of the acceptors. The HOMOs are localized on the donor moieties, and the LUMOs on the acceptor moieties. The introduction of low-cost Fe and Ti to the free-base porphyrin leads to more active nonlinear optical performance, stronger response to the external electric field, and induces higher photo-to-current conversion efficiency. They also red shift the absorption bands of the free-base porphyrin, and make it a potential candidate for harvesting light in the entire UV–Vis region of solar spectrum. Size ranges: dyes (0.1–1 nm) and pore diameters of a dye-sensitized mesoporous film of TiO2 (2–50 nm).

Effect of metal oxide morphology on electron injection from CdSe quantum dots to ZnO

Performance of quantum dot sensitized solar cells relies on a rapid electron injection from quantum dot to metal oxide. We studied the injection process in CdSe-ZnO system by ultrafast time-resolved absorption spectroscopy for two types of acceptor morphologies—nanowires and nanoparticles' films. Based on comparison between experimental data and Marcus theory, we demonstrate that the acceptor morphology has a significant impact on electron injection due to (i) change in material permittivity and (ii) different density of the band-edge states. The results open a reference to improve injection efficiency in quantum dot-metal oxide system by selection of the acceptor morphology.