Bichromatic circularly polarized fields provide a useful tool to probe the ionization dynamics.In this work, we compare the photoelectron momentum distribution in few-cycle bichromatic field of different helicities.Th...Bichromatic circularly polarized fields provide a useful tool to probe the ionization dynamics.In this work, we compare the photoelectron momentum distribution in few-cycle bichromatic field of different helicities.The spectral features are analyzed with semiclassical trajectories derived from the strong field approximation.In particular, the interference fringes in momentum distribution are investigated by tracking the ionization time and tunneling exits of released photoelectrons.Different types of trajectories that contribute to the interference fringes are elucidated.展开更多
Anchoring molecular cocatalysts on semiconductors has been recognized as a general strategy to boost the charge separation efficiency required for efficient photocatalysis.However,the effect of molecular cocatalysts o...Anchoring molecular cocatalysts on semiconductors has been recognized as a general strategy to boost the charge separation efficiency required for efficient photocatalysis.However,the effect of molecular cocatalysts on energy funneling(i.e.,directional energy transfer)inside semiconductor photocatalysts has not been demonstrated yet.Here we prepared CdS nanorods with both thin and thick rods and anchored the conjugated molecules 2‐mercaptobenzimidazole(MBI)and cobalt molecular catalysts(MCoA)sequentially onto the surface of nanorods.Transient absorption measurements revealed that MBI molecules facilitated energy funneling from thin to thick rods by the electronic coupling between thin and thick nanorods,which is essentially a light‐harvesting antenna approach to enhance the charge generation efficiency in the reaction center(here the thick rods).Moreover,MBI and MCoA molecules selectively extracted photogenerated holes and electrons of CdS nanorods rapidly,leading to efficient charge separation.Consequently,CdS/MBI/MCoA displayed 15 times enhanced photocatalytic H_(2) evolution(1.65 mL)than pure CdS(0.11 mL)over 3 h of illumination.The amount of H_(2) evolution reached 60 mL over 48 h of illumination with a high turnover number of 26294 and an apparent quantum efficiency of 71%at 420 nm.This study demonstrates a novel design principle for next‐generation photocatalysts.展开更多
The dielectric confinement effect plays an essential role in optoelectronic devices.Existing studies on the relationship between the dielectric confinement and the photoelectric properties are inadequate.Herein,three ...The dielectric confinement effect plays an essential role in optoelectronic devices.Existing studies on the relationship between the dielectric confinement and the photoelectric properties are inadequate.Herein,three organic spacers with different dielectric constants are employed to tune the exciton dynamics of quasi-two-dimensional(quasi-2D)Ruddlesden–Popper perovskite films.Femtosecond transient absorption spectroscopy reveals that the small dielectric constant ligand enables a weak dynamic disorder and a large modulation depth of the coherent phonons,resulting in a more complete energy transfer and the inhibition of a trap-mediated nonradiative recombination.Additionally,the increase in the bulk-ligand dielectric constant reduces the corresponding exciton binding energy and then suppresses the Auger recombination,which is beneficial for high-luminance lightemitting diodes.This work emphasizes the importance of dielectric confinement for regulating the exciton dynamics of layered perovskites.展开更多
Organic-inorganic layered perovskites are two-dimensional quantum well layers in which the layers of lead halide octahedra are stacked between the organic cation layers.The packing geometry of the soft organic molecul...Organic-inorganic layered perovskites are two-dimensional quantum well layers in which the layers of lead halide octahedra are stacked between the organic cation layers.The packing geometry of the soft organic molecules and the stiff ionic crystals induce structural deformation of the inorganic octahedra,generating complex lattice dynamics.Especially,the dielectric confinement and ionic sublattice lead to strong coupling between the photogenerated excitons and the phonons from the polar lattice which intensively affects the properties for device applications.The anharmonicity and dynamic disorder from the organic cations participate in the relaxation dynamics coupled with excitations.However,a detailed understanding of this underlying mechanism remains obscure.This work investigates the electron–optical phonon coupling dynamics by employing ultrafast pump-probe transient absorption spectroscopy.The activated different optical phonon modes are observed via systematic studies of(PEA)_(2)PbBr_(4) perovskite films on the ultrafast lattice vibrational dynamics.The experimental results indicate that solvent engineering has a significant influence on lattice vibrational modes and coherent phonon dynamics.This work provides fresh insights into electron-optical phonon coupling for emergent optoelectronics development based on layered perovskites.展开更多
A comprehensive understanding of excited-state dynamics of semiconductor quantum dots or nanomaterials at the atomic or molecular level is of scientific importance.Pure inorganic(or non-covalently protected)seimicondu...A comprehensive understanding of excited-state dynamics of semiconductor quantum dots or nanomaterials at the atomic or molecular level is of scientific importance.Pure inorganic(or non-covalently protected)seimiconductor molecular nanoclusters with atomically precise structure are contributive to establish accurate correlation of excited-state dynamics with their composition/structure,however,the related studies are almost blank because of unresolved solvent dispersion issue.Herein,we designedly created the largest discrete chalcogenide seimiconductor molecular nanoclusters(denoted P2-CuMSnS,M=In or/and Ga)with great dispersibility,and revealed an interesting intracluster“core–shell”charge transfer relaxation dynamics.A systematic red shift in absorption spectra with the gradual substitution of In by Ga was experimentally and computationally investigated,and femtosecond transient absorption measurements further manifested there were three ultrafast processes in excited-state dynamics of P2 nanoclusters with the corresponding amplitudes directed by composition variation.Current results hold the great promise of the solution-processible applications of semiconductor-NC-based quantum dots and facilitate the development of atomically precise nano-chemistry.展开更多
Suppressing the trap-state density and the energy loss via ternary strategy was demonstrated.Favorable vertical phase distribution with donors(acceptors)accumulated(depleted)at the interface of active layer and charge...Suppressing the trap-state density and the energy loss via ternary strategy was demonstrated.Favorable vertical phase distribution with donors(acceptors)accumulated(depleted)at the interface of active layer and charge extraction layer can be obtained by introducing appropriate amount of polymer acceptor N2200 into the systems of PBDB-T:IT-M and PBDB-TF:Y6.In addition,N2200 is gradiently distributed in the vertical direction in the ternary blend film.Various measurements were carried out to study the effects of N2200 on the binary systems.It was found that the optimized morphology especially in vertical direction can significantly decrease the trap state density of the binary blend films,which is beneficial for the charge transport and collection.All these features enable an obvious decrease in charge recombination in both PBDB-T:IT-M and PBDB-TF:Y6 based organic solar cells(OSCs),and power conversion efficiencies(PCEs)of 12.5%and 16.42%were obtained for the ternary OSCs,respectively.This work indicates that it is an effective method to suppress the trap state density and thus improve the device performance through ternary strategy.展开更多
The donor:acceptor(D:A) blend ratio plays a very important role in affecting the progress of charge transfer and energy transfer in bulk heterojunction(BHJ) orga nic solar cells(OSCs).The proper D:A blend ratio can pr...The donor:acceptor(D:A) blend ratio plays a very important role in affecting the progress of charge transfer and energy transfer in bulk heterojunction(BHJ) orga nic solar cells(OSCs).The proper D:A blend ratio can provide maximized D/A interfacial area for exciton dissociation and appro p riate domain size of the exciton diffusion length,which is beneficial to obtain high-performance OSCs.Here,we comprehensively investigated the relationship between various D:A blend ratios and the charge transfer and energy transfer mechanisms in OSCs based on PBDB-T and non-fullerene acceptor IT-M.Based on various D:A blend ratios,it was found that the ratio of components is a key factor to suppress the formation of triplet states and recombination energy losses.Rational D:A blend ratios can provide appropriate donor/accepter surface for charge transfer which has been powerfully verified by various detailed experimental results from the time-resolved fluorescence measurement and transient absorption(TA) spectroscopy.Optimized coherence length and crystallinity are verified by grazing incident wide-angle X-ray scattering(GIWAXS) measurements.The results are bene ficial to comprehend the effects of various D:A blend ratios on charge transfer and energy transfer dynamics and provides constructive suggestions for rationally designing new materials and feedback for photovoltaic performance optimization in non-fullerene OSCs.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11420101003,11604347,11827806,11874368,61675213,and 91636105)
文摘Bichromatic circularly polarized fields provide a useful tool to probe the ionization dynamics.In this work, we compare the photoelectron momentum distribution in few-cycle bichromatic field of different helicities.The spectral features are analyzed with semiclassical trajectories derived from the strong field approximation.In particular, the interference fringes in momentum distribution are investigated by tracking the ionization time and tunneling exits of released photoelectrons.Different types of trajectories that contribute to the interference fringes are elucidated.
文摘Anchoring molecular cocatalysts on semiconductors has been recognized as a general strategy to boost the charge separation efficiency required for efficient photocatalysis.However,the effect of molecular cocatalysts on energy funneling(i.e.,directional energy transfer)inside semiconductor photocatalysts has not been demonstrated yet.Here we prepared CdS nanorods with both thin and thick rods and anchored the conjugated molecules 2‐mercaptobenzimidazole(MBI)and cobalt molecular catalysts(MCoA)sequentially onto the surface of nanorods.Transient absorption measurements revealed that MBI molecules facilitated energy funneling from thin to thick rods by the electronic coupling between thin and thick nanorods,which is essentially a light‐harvesting antenna approach to enhance the charge generation efficiency in the reaction center(here the thick rods).Moreover,MBI and MCoA molecules selectively extracted photogenerated holes and electrons of CdS nanorods rapidly,leading to efficient charge separation.Consequently,CdS/MBI/MCoA displayed 15 times enhanced photocatalytic H_(2) evolution(1.65 mL)than pure CdS(0.11 mL)over 3 h of illumination.The amount of H_(2) evolution reached 60 mL over 48 h of illumination with a high turnover number of 26294 and an apparent quantum efficiency of 71%at 420 nm.This study demonstrates a novel design principle for next‐generation photocatalysts.
基金the National Natural Science Foundation of China(22378148,21975084,51672089)the Natural Science Foundation of Guangdong Province(2021A1515010075)for their supports。
基金the support of all the technicians at Henan Normal University and Henan Universitysupported by Zhongyuan Scholar of Henan Province(224000510007)+2 种基金the National Natural Science Foundation of China(11974103)for fundingthe financial support from the AXA research fundthe funding from Henan Province College Youth Backbone Teacher Project(2020GGJS062)。
基金National Natural Science Foundation of China(12347158,11804084,12074104,61627818,U1804261)Natural Science Foundation of Henan Province(222300420057)Young Backbone Teacher Training Program in Higher Education of Henan Province(2019GGJS065)。
文摘The dielectric confinement effect plays an essential role in optoelectronic devices.Existing studies on the relationship between the dielectric confinement and the photoelectric properties are inadequate.Herein,three organic spacers with different dielectric constants are employed to tune the exciton dynamics of quasi-two-dimensional(quasi-2D)Ruddlesden–Popper perovskite films.Femtosecond transient absorption spectroscopy reveals that the small dielectric constant ligand enables a weak dynamic disorder and a large modulation depth of the coherent phonons,resulting in a more complete energy transfer and the inhibition of a trap-mediated nonradiative recombination.Additionally,the increase in the bulk-ligand dielectric constant reduces the corresponding exciton binding energy and then suppresses the Auger recombination,which is beneficial for high-luminance lightemitting diodes.This work emphasizes the importance of dielectric confinement for regulating the exciton dynamics of layered perovskites.
基金supported by the National Natural Science Foundation of China(Nos.U1804261,61627818,12074104,11804084,62075058,and 11827806)Natural Science Foundation of Henan Province(No.222300420057)+1 种基金the Outstanding Youth Foundation of Henan Normal University(No.20200171)the Young Backbone Teacher Training Program in Higher Education of Henan Province(No.2019GGJS065).
文摘Organic-inorganic layered perovskites are two-dimensional quantum well layers in which the layers of lead halide octahedra are stacked between the organic cation layers.The packing geometry of the soft organic molecules and the stiff ionic crystals induce structural deformation of the inorganic octahedra,generating complex lattice dynamics.Especially,the dielectric confinement and ionic sublattice lead to strong coupling between the photogenerated excitons and the phonons from the polar lattice which intensively affects the properties for device applications.The anharmonicity and dynamic disorder from the organic cations participate in the relaxation dynamics coupled with excitations.However,a detailed understanding of this underlying mechanism remains obscure.This work investigates the electron–optical phonon coupling dynamics by employing ultrafast pump-probe transient absorption spectroscopy.The activated different optical phonon modes are observed via systematic studies of(PEA)_(2)PbBr_(4) perovskite films on the ultrafast lattice vibrational dynamics.The experimental results indicate that solvent engineering has a significant influence on lattice vibrational modes and coherent phonon dynamics.This work provides fresh insights into electron-optical phonon coupling for emergent optoelectronics development based on layered perovskites.
基金The authors acknowledge financial support from the National Natural Science Foundation of China(Nos.21671142,11804084 and 21875150)the Jiangsu Province Natural Science Fund for Distinguished Young Scholars(No.BK20160006)+2 种基金the 111 Project(No.D20015)the Project of Scientific and Technologic Infrastructure of Suzhou(No.SZS201905)the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD).The authors also thank Dr.D.C.Ma at Analytical and Testing Center,Sichuan University for technical help with the Material Studio calculations.
文摘A comprehensive understanding of excited-state dynamics of semiconductor quantum dots or nanomaterials at the atomic or molecular level is of scientific importance.Pure inorganic(or non-covalently protected)seimiconductor molecular nanoclusters with atomically precise structure are contributive to establish accurate correlation of excited-state dynamics with their composition/structure,however,the related studies are almost blank because of unresolved solvent dispersion issue.Herein,we designedly created the largest discrete chalcogenide seimiconductor molecular nanoclusters(denoted P2-CuMSnS,M=In or/and Ga)with great dispersibility,and revealed an interesting intracluster“core–shell”charge transfer relaxation dynamics.A systematic red shift in absorption spectra with the gradual substitution of In by Ga was experimentally and computationally investigated,and femtosecond transient absorption measurements further manifested there were three ultrafast processes in excited-state dynamics of P2 nanoclusters with the corresponding amplitudes directed by composition variation.Current results hold the great promise of the solution-processible applications of semiconductor-NC-based quantum dots and facilitate the development of atomically precise nano-chemistry.
基金supported by the National Natural Science Foundation of China(21835006,21704004)the Fundamental Research Funds for the Central Universities,China(FRF-TP-19-047A2)China Postdoctoral Science Foundation(2019M660799)。
文摘Suppressing the trap-state density and the energy loss via ternary strategy was demonstrated.Favorable vertical phase distribution with donors(acceptors)accumulated(depleted)at the interface of active layer and charge extraction layer can be obtained by introducing appropriate amount of polymer acceptor N2200 into the systems of PBDB-T:IT-M and PBDB-TF:Y6.In addition,N2200 is gradiently distributed in the vertical direction in the ternary blend film.Various measurements were carried out to study the effects of N2200 on the binary systems.It was found that the optimized morphology especially in vertical direction can significantly decrease the trap state density of the binary blend films,which is beneficial for the charge transport and collection.All these features enable an obvious decrease in charge recombination in both PBDB-T:IT-M and PBDB-TF:Y6 based organic solar cells(OSCs),and power conversion efficiencies(PCEs)of 12.5%and 16.42%were obtained for the ternary OSCs,respectively.This work indicates that it is an effective method to suppress the trap state density and thus improve the device performance through ternary strategy.
基金supported by the National Natural Science Foundation of China(Nos.11774204,11804084)Major Program of Natural Science Foundation 25 of Shandong Province(No.ZR2019ZD43)+2 种基金the Fundamental Research Funds of Shandong University(No.2018JC034)support from the ARC Centre of Excellence in Exciton Science(No.CE170100026)the Shanghai Synchrotron Radiation Facility(beamline BL16B1)for providing the beam time for GIWAXS measurements。
文摘The donor:acceptor(D:A) blend ratio plays a very important role in affecting the progress of charge transfer and energy transfer in bulk heterojunction(BHJ) orga nic solar cells(OSCs).The proper D:A blend ratio can provide maximized D/A interfacial area for exciton dissociation and appro p riate domain size of the exciton diffusion length,which is beneficial to obtain high-performance OSCs.Here,we comprehensively investigated the relationship between various D:A blend ratios and the charge transfer and energy transfer mechanisms in OSCs based on PBDB-T and non-fullerene acceptor IT-M.Based on various D:A blend ratios,it was found that the ratio of components is a key factor to suppress the formation of triplet states and recombination energy losses.Rational D:A blend ratios can provide appropriate donor/accepter surface for charge transfer which has been powerfully verified by various detailed experimental results from the time-resolved fluorescence measurement and transient absorption(TA) spectroscopy.Optimized coherence length and crystallinity are verified by grazing incident wide-angle X-ray scattering(GIWAXS) measurements.The results are bene ficial to comprehend the effects of various D:A blend ratios on charge transfer and energy transfer dynamics and provides constructive suggestions for rationally designing new materials and feedback for photovoltaic performance optimization in non-fullerene OSCs.
