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Fast interfacial charge transfer in ?-Fe₂O_3-?C_?/FeVO_4-x+?C_x-?@C bulk heterojunctions with controllable phase content.

ABSTRACT: The novelties in this paper are embodied in the fast interfacial charge transfer in ?-Fe₂O_3-?C_?/FeVO_4-x+?C_x-?@C bulk heterojunctions with controllable phase compositions. The carbon source-glucose plays an important role as the connecting bridge between the micelles in the solution, forming interfacial C-O, C-O-Fe and O-Fe-C bonds through dehydration and polymerization reactions. Then the extra VO₃^- around the FeVO₄ colloidal particles can react with unstable Fe(OH)₃, resulting the phase transformation from ?-Fe₂O₃ (47.99-7.16%) into FeVO₄ (52.01-92.84%), promoting photocarriers' generation capacities. After final carbonization, a part of C atoms enter into lattices of ?-Fe₂O₃ and FeVO₄, forming impurity levels and oxygen vacancies to increase effective light absorptions. Another part of C sources turn into interfacial carbon layers to bring fast charge transfer by decreasing the charge transition resistance (from 53.15?k? into 8.29?k?) and the surface recombination rate (from 64.07% into 7.59%). The results show that the bulk heterojunction with 90.29% FeVO₄ and 9.71% ?-Fe₂O₃ shows ideal light absorption, carriers' transfer efficiency and available photocatalytic property. In general, the synergistic effect of optimized heterojunction structure, carbon replacing and the interface carbon layers are critical to develop great potential in stable and recoverable use.

SUBMITTER: Zhao C

PROVIDER: S-EPMC5141511 | biostudies-literature | 2016 Dec

REPOSITORIES: biostudies-literature

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Fast interfacial charge transfer in α-Fe2O3-δCδ/FeVO4-x+δCx-δ@C bulk heterojunctions with controllable phase content.

Zhao Chengcheng C Tan Guoqiang G Yang Wei W Xu Chi C Liu Ting T Su Yuning Y Ren Huijun H Xia Ao A

Scientific reports 20161207

The novelties in this paper are embodied in the fast interfacial charge transfer in α-Fe2O3-δCδ/FeVO4-x+δCx-δ@C bulk heterojunctions with controllable phase compositions. The carbon source-glucose plays an important role as the connecting bridge between the micelles in the solution, forming interfacial C-O, C-O-Fe and O-Fe-C bonds through dehydration and polymerization reactions. Then the extra VO3- around the FeVO ...[more]

PMID: 27924929

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Project description:The ongoing depletion of fossil fuels has led to an intensive search for additional renewable energy sources. Solar-based technologies could provide sufficient energy to satisfy the global economic demands in the near future. Photovoltaic (PV) cells are the most promising man-made devices for direct solar energy utilization. Understanding the charge separation and charge transport in PV materials at a molecular level is crucial for improving the efficiency of the solar cells. Here, we use light-induced EPR spectroscopy combined with DFT calculations to study the electronic structure of charge separated states in blends of polymers (P3HT, PCDTBT, and PTB7) and fullerene derivatives (C60-PCBM and C70-PCBM). Solar cells made with the same composites as active layers show power conversion efficiencies of 3.3% (P3HT), 6.1% (PCDTBT), and 7.3% (PTB7), respectively. Upon illumination of these composites, two paramagnetic species are formed due to photo-induced electron transfer between the conjugated polymer and the fullerene. They are the positive, P(+), and negative, P(-), polarons on the polymer backbone and fullerene cage, respectively, and correspond to radical cations and radical anions. Using the high spectral resolution of high-frequency EPR (130 GHz), the EPR spectra of these species were resolved and principal components of the g-tensors were assigned. Light-induced pulsed ENDOR spectroscopy allowed the determination of (1)H hyperfine coupling constants of photogenerated positive and negative polarons. The experimental results obtained for the different polymer-fullerene composites have been compared with DFT calculations, revealing that in all three systems the positive polaron is distributed over distances of 40-60 Å on the polymer chain. This corresponds to about 15 thiophene units for P3HT, approximately three units for PCDTBT, and about three to four units for PTB7. No spin density delocalization between neighboring fullerene molecules was detected by EPR. Strong delocalization of the positive polaron on the polymer donor is an important reason for the efficient charge separation in bulk heterojunction systems as it minimizes the wasteful process of charge recombination. The combination of advanced EPR spectroscopy and DFT is a powerful approach for investigation of light-induced charge dynamics in organic photovoltaic materials.

Dataset Information

Fast interfacial charge transfer in ?-Fe₂O_3-?C_?/FeVO_4-x+?C_x-?@C bulk heterojunctions with controllable phase content.

Publications

Fast interfacial charge transfer in α-Fe<sub>2</sub>O<sub>3-δ</sub>C<sub>δ</sub>/FeVO<sub>4-x+δ</sub>C<sub>x-δ</sub>@C bulk heterojunctions with controllable phase content.

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Dataset Information

Fast interfacial charge transfer in ?-Fe2O3-?C?/FeVO4-x+?Cx-?@C bulk heterojunctions with controllable phase content.

Publications

Fast interfacial charge transfer in α-Fe<sub>2</sub>O<sub>3-δ</sub>C<sub>δ</sub>/FeVO<sub>4-x+δ</sub>C<sub>x-δ</sub>@C bulk heterojunctions with controllable phase content.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

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Fast interfacial charge transfer in ?-Fe₂O_3-?C_?/FeVO_4-x+?C_x-?@C bulk heterojunctions with controllable phase content.