Facilitated interfacial charge separation using triphenylamine-zinc porphyrin dyad-sensitized TiO2 nanoparticles for photocatalysis

Interfacial charge-transfer (ICT) transitions involved in charge-separation mechanisms are expected to enable efficient photovoltaic conversions through one-step charge-separation processes. With this in mind, the charge-transfer complex fabricated from TiO2 nanoparticles and 7,7,8,8-tetracyanoquinodimethane (TCNQ) has been applied to dye-sensitized solar cells. However, rapid carrier recombination from the conduction band of TiO2 to the highest occupied molecular orbital (HOMO) of TCNQ remains a major issue for this complex. In this study, to inhibit surface-complex recombinations, we prepared Nb-doped TiO2 nanoparticles with different atomic ratios for enhanced electron transport. To investigate the effects of doping on electron injection through ICT transitions, these materials were examined as photoelectrodes. When TiO2 was doped with 1.5 mol % Nb, the Fermi level of the TiO2 electrode shifted toward the conduction band minimum, which improved electron back-contact toward the HOMO of TCNQ. The enhancement in electron transport led to increases in both short circuit current and open circuit voltage, resulting in a slight (1.1% to 1.3%) improvement in photovoltaic conversion efficiency compared to undoped TiO2. Such control of electron transport within the photoelectrode is attributed to improvements in electron injection through ICT transitions.

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Anion-enhanced excited state charge separation in a spiro-locked N-heterocycle-fused push-pull zinc porphyrin

Chemical Science ◽

10.1039/d1sc00038a ◽

2021 ◽

Author(s):

Mandeep K. Chahal ◽

Anuradha Liyanage ◽

Ajyal Z. Alsaleh ◽

Paul A. Karr ◽

Jonathan P. Hill ◽

...

Keyword(s):

Excited State ◽

Charge Transfer ◽

Charge Separation ◽

Charge Transfer Complex ◽

Zinc Porphyrin ◽

New Type ◽

State Charge

A new type of push–pull charge transfer complex, viz., a spiro-locked N-heterocycle-fused zinc porphyrin, ZnP-SQ, is shown to undergo excited state charge separation, which is enhanced by axial F− binding to the Zn center.

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Long-lived charge separation following pump-wavelength–dependent ultrafast charge transfer in graphene/WS2 heterostructures

Science Advances ◽

10.1126/sciadv.abd9061 ◽

2021 ◽

Vol 7 (9) ◽

pp. eabd9061

Author(s):

Shuai Fu ◽

Indy du Fossé ◽

Xiaoyu Jia ◽

Jingyin Xu ◽

Xiaoqing Yu ◽

...

Keyword(s):

Charge Transfer ◽

Charge Separation ◽

Transient Absorption ◽

Transition Metal Dichalcogenides ◽

Thermionic Emission ◽

Great Promise ◽

Metal Dichalcogenides ◽

Ultrafast Charge Transfer ◽

Device Operation ◽

Interfacial Charge

Van der Waals heterostructures consisting of graphene and transition metal dichalcogenides have shown great promise for optoelectronic applications. However, an in-depth understanding of the critical processes for device operation, namely, interfacial charge transfer (CT) and recombination, has so far remained elusive. Here, we investigate these processes in graphene-WS2 heterostructures by complementarily probing the ultrafast terahertz photoconductivity in graphene and the transient absorption dynamics in WS2 following photoexcitation. We observe that separated charges in the heterostructure following CT live extremely long: beyond 1 ns, in contrast to ~1 ps charge separation reported in previous studies. This leads to efficient photogating of graphene. Furthermore, for the CT process across graphene-WS2 interfaces, we find that it occurs via photo-thermionic emission for sub-A-exciton excitations and direct hole transfer from WS2 to the valence band of graphene for above-A-exciton excitations. These findings provide insights to further optimize the performance of optoelectronic devices, in particular photodetection.

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Photoexcited charge carrier dynamics of interconnected TiO2 nanoparticles: evidence of enhancement of charge separation at anatase–rutile particle interfaces

Physical Chemistry Chemical Physics ◽

10.1039/c7cp07563d ◽

2018 ◽

Vol 20 (5) ◽

pp. 3484-3489 ◽

Cited By ~ 15

Author(s):

Daiki Shingai ◽

Yusuke Ide ◽

Woon Yong Sohn ◽

Kenji Katayama

Keyword(s):

Charge Carrier ◽

Tio2 Nanoparticles ◽

Hydrothermal Treatment ◽

Charge Separation ◽

Separation Efficiency ◽

Carrier Dynamics ◽

Charge Carrier Dynamics ◽

Charge Separation Efficiency ◽

Photoexcited Charge Carrier

Hydrothermal treatment can improve the charge separation efficiency of P25.

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Efficient photocatalytic H2 evolution using NiS/ZnIn2S4 heterostructures with enhanced charge separation and interfacial charge transfer

Applied Catalysis B Environmental ◽

10.1016/j.apcatb.2019.02.075 ◽

2019 ◽

Vol 250 ◽

pp. 163-170 ◽

Cited By ~ 43

Author(s):

Aihua Yan ◽

Xiaowei Shi ◽

Fei Huang ◽

Mamoru Fujitsuka ◽

Tetsuro Majima

Keyword(s):

Charge Transfer ◽

Charge Separation ◽

H2 Evolution ◽

Interfacial Charge Transfer ◽

Interfacial Charge ◽

Photocatalytic H2 Evolution

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Stabilization of charge separation in a zinc porphyrin-viologen-quinone triad

Bulletin of the Academy of Sciences of the USSR Division of Chemical Science ◽

10.1007/bf00962375 ◽

1990 ◽

Vol 39 (6) ◽

pp. 1156-1159

Author(s):

E. E. Batova ◽

P. P. Levin ◽

V. Ya. Shafirovich

Keyword(s):

Charge Separation ◽

Zinc Porphyrin

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Cover Picture: Geometry-Controlled Photoinduced Charge Separation and Recombination in a Trans -A2 B2 -Functionalized Donor-Acceptor Conjugate Composed of a Multimodular Zinc Porphyrin and Fullerene (ChemPhotoChem 1/2017)

ChemPhotoChem ◽

10.1002/cptc.201600053 ◽

2017 ◽

Vol 1 (1) ◽

pp. 1-1

Author(s):

Alejandro Benitz ◽

Michael B. Thomas ◽

Francis D'Souza

Keyword(s):

Charge Separation ◽

Zinc Porphyrin ◽

Photoinduced Charge Separation ◽

Donor Acceptor ◽

Photoinduced Charge

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Accelerated Charge Separation and Stabilization in a Fused Bis Zinc Porphyrin-Quinone Conjugate Via Cation-Quinone Interaction

ECS Meeting Abstracts ◽

10.1149/ma2019-01/14/947 ◽

2019 ◽

Keyword(s):

Charge Separation ◽

Zinc Porphyrin ◽

Accelerated Charge

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Long-lived and disorder-free charge transfer states enable endothermic charge separation in efficient non-fullerene organic solar cells

Nature Communications ◽

10.1038/s41467-020-19332-5 ◽

2020 ◽

Vol 11 (1) ◽

Cited By ~ 1

Author(s):

Ture F. Hinrichsen ◽

Christopher C. S. Chan ◽

Chao Ma ◽

David Paleček ◽

Alexander Gillett ◽

...

Keyword(s):

Solar Cells ◽

Charge Transfer ◽

Organic Solar Cells ◽

Charge Separation ◽

Free Charge ◽

Charge Generation ◽

Time Resolved ◽

Thermodynamic Conditions ◽

Donor Acceptor ◽

Interfacial Charge

Abstract Organic solar cells based on non-fullerene acceptors can show high charge generation yields despite near-zero donor–acceptor energy offsets to drive charge separation and overcome the mutual Coulomb attraction between electron and hole. Here, we use time-resolved optical spectroscopy to show that free charges in these systems are generated by thermally activated dissociation of interfacial charge-transfer states that occurs over hundreds of picoseconds at room temperature, three orders of magnitude slower than comparable fullerene-based systems. Upon free electron–hole encounters at later times, both charge-transfer states and emissive excitons are regenerated, thus setting up an equilibrium between excitons, charge-transfer states and free charges. Our results suggest that the formation of long-lived and disorder-free charge-transfer states in these systems enables them to operate closely to quasi-thermodynamic conditions with no requirement for energy offsets to drive interfacial charge separation and achieve suppressed non-radiative recombination.

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