Photochemically Driven Modulated Charge Transfer at Local Contacts between CH3NH3PbI3 and Carboxylated Multiwalled Carbon Nanotubes

Prajongtat, Pongthep; Wargulski, Dan R.; Unold, Thomas; Dittrich, Thomas

doi:10.1021/acs.jpcc.5b11854

Cited by 8 publications

(9 citation statements)

References 30 publications

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“…Because holes are transported through HOMOs, the relative orientation between the HOMOs of PT and perovskite as a result of different PT orientations becomes the key for solar cell performance. According to previously studied HOMOs of both P3HT and lead iodine-based perovskite, , they would overlap better with a lying down PT thiophene backbone orientation. Therefore, an edge-on thiophene backbone would lead to a greater offset of HOMO–HOMO between perovskite and PTs.…”

Section: Resultsmentioning

confidence: 99%

Effect of Interfacial Molecular Orientation on Power Conversion Efficiency of Perovskite Solar Cells

et al. 2017

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A wide variety of charge carrier dynamics, such as transport, separation, and extraction, occur at the interfaces of planar heterojunction solar cells. Such factors can affect the overall device performance. Therefore, understanding the buried interfacial molecular structure in various devices and the correlation between interfacial structure and function has become increasingly important. Current characterization techniques for thin films such as X-ray diffraction, cross section scanning electronmicroscopy, and UV-visible absorption spectroscopy are unable to provide the needed molecular structural information at buried interfaces. In this study, by controlling the structure of the hole transport layer (HTL) in a perovskite solar cell and applying a surface/interface-sensitive nonlinear vibrational spectroscopic technique (sum frequency generation vibrational spectroscopy (SFG)), we successfully probed the molecular structure at the buried interface and correlated its structural characteristics to solar cell performance. Here, an edge-on (normal to the interface) polythiophene (PT) interfacial molecular orientation at the buried perovskite (photoactive layer)/PT (HTL) interface showed more than two times the power conversion efficiency (PCE) of a lying down (tangential) PT interfacial orientation. The difference in interfacial molecular structure was achieved by altering the alkyl side chain length of the PT derivatives, where PT with a shorter alkyl side chain showed an edge-on interfacial orientation with a higher PCE than that of PT with a longer alkyl side chain. With similar band gap alignment and bulk structure within the PT layer, it is believed that the interfacial molecular structural variation (i.e., the orientation difference) of the various PT derivatives is the underlying cause of the difference in perovskite solar cell PCE.

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Section: Resultsmentioning

confidence: 99%

Effect of Interfacial Molecular Orientation on Power Conversion Efficiency of Perovskite Solar Cells

et al. 2017

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“…Similar to T/BV, the SS-SPS response of 7Ag-T/BV is gradually enhanced with increasing the content of O 2 ( Figure S3), indicating that the presence of O 2 is favorable for charge separation by capturing electrons. 8,22 The kinetic manners of photogenerated electrons and holes are studied by TS-SPV in N 2 . Generally speaking, the TS-SPV response is involved with two time ranges: fast (<10 −5 s) from the charge separation by the built-in electric field, and slow (>10 −4 s) from the charge diffusion process.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Accepting Excited High-Energy-Level Electrons and Catalyzing H₂ Evolution of Dual-Functional Ag-TiO₂ Modifier for Promoting Visible-Light Photocatalytic Activities of Nanosized Oxides

Bian

Raziq

et al. 2016

J. Phys. Chem. C

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To improve the photocatalytic activities of narrow band gap oxide semiconductors for H 2 evolution under solar irradiation, it is highly desired to develop effective acceptors for visible light-excited high-energy-level electrons. Herein, we have successfully fabricated Ag-modified TiO 2 /BiVO 4 nanocomposites by putting nanosized BiVO 4 into the Ag modified TiO 2 sol. Both steady-state and transient-statesurface photovoltage spectra demonstrate that photogenerated charge separation and lifetime of nanosized BiVO 4 is promoted when coupling with TiO 2 and modifying an appropriate amount of Ag, while the lifetime of photogenerated electrons got prolonged. Interestingly, the resulting Ag-TiO 2 /BiVO 4 nanocomposites exhibit excellent visible light activities for H 2 evolution, although the visible light activities of TiO 2 /BiVO 4 one, Ag/BiVO 4 and bare BiVO 4 are neglectable, indicating that AgTiO 2 could be utilized as effective acceptors for hydrogen production. It is suggested based on the experimental data that the effective acceptors be attributed to the used TiO 2 for accepting the high-energy-level electrons generated from BiVO 4 and to the modified Ag for being reduced then to catalyze H 2 -evolution reactions. The developed strategy is versatile for other narrow band gap semiconductors, like WO 3 and Fe 2 O 3 . ■ INTRODUCTIONPhotocatalytic hydrogen evolution is regarded as a potential technique that can solve the current increasingly serious energy crisis through effective solar utilization. 1 Despite a great deal of effort made, the quantum efficiencies of state-of-art works are still low, far from the practical requirement for industrialization. 2,3 Photocatalytic reactions for H 2 evolution are mainly involved with complex thermodynamics and kinetic processes. In general, efficient photocatalysts are needed to possess strong solar-light absorption, high charge separation and superior catalytic capacity. It is well-known that cheap, stable, and environment friendly narrow band gap oxide semiconductors, such as BiVO 4 , Fe 2 O 3 , and WO 3 , can greatly absorb solar light, and the electrons will be excited from valence band (VB) to conduction band (CB) bottom and even over the level under solar irradiation. 4−6 The excited electrons at much higher energy level than the CB bottom usually relax to the CB bottom quite quickly (within picosecond time scale). 7,8 Since their CB bottom levels are usually located below 0 eV versus NHE, 9 so that the excited electrons are not suitable for energetic H 2 evolution, it is understandable that such narrowband gap oxides always exhibit low photocatalytic activities. However, it is worth noting that those visible-light-excited highenergy-level (HEL) electrons would naturally possess strong capacity to induce reduction reactions with water molecules thermodynamically. 10,11 For this, the key would be how to prolong the lifetimes of HEL electrons by altering the fast relaxation process. Unfortunately, it has seldom been reported until now.Constructing a heterojuntional ...

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“…Figure shows in-phase and phase-shifted by 90° SPV spectra for the organic lead iodide complex and MAPbI 3 containing 3.85 mol % AVAI. The sign of the in-phase SPV signal can be used to explain the direction of charge separation within the samples. , For the organic lead iodide complex, the in-phase SPV signal was negative and its maximum was observed to be −0.21 mV at a photon energy of 2.82 eV. This means that photogenerated electrons were separated preferentially toward the external surface.…”

Section: Resultsmentioning

confidence: 99%

A Combined Theoretical and Experimental Study of CH₃NH₃PbI₃ Containing AVAI Films Prepared via an Intramolecular Exchange Process

Prajongtat

Hannongbua

2018

J. Phys. Chem. C

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Methylammonium lead iodide (CH3NH3PbI3) has emerged as a superior light-absorbing material for perovskite solar cells, mainly because of its excellent optical and electronic properties. However, insufficient long-term stability of CH3NH3PbI3 has severely hindered its practical applications. The direct addition of 5-ammonium valeric acid iodide (HOOC(CH2)4NH3I or AVAI) to perovskite precursors, such as CH3NH3I and PbI2, was found to improve the stability of CH3NH3PbI3, but can limit the incorporation of AVA+ into the CH3NH3PbI3 structure because of strong competitive interactions between AVA+ and CH3NH3 + with PbI2 through the same electrostatic interactions. Here, we present an alternative approach to prepare high-quality CH3NH3PbI3 containing AVAI films via an intramolecular exchange process. The films were prepared from precursor complexes, that is, organic lead iodide complexes, by the intramolecular exchange of dimethyl sulfoxide intercalated in the complexes with CH3NH3 +. Scanning electron microscopy, grazing-incidence X-ray diffraction, and modulated surface photovoltage spectroscopy were employed to characterize morphological and electronic properties of the prepared materials. To gain a deeper understanding of the formation and stability of organic lead iodide complexes and perovskite, the structures, binding strength, and formation energies of these materials were investigated by density functional theory calculations.

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Photochemically Driven Modulated Charge Transfer at Local Contacts between CH₃NH₃PbI₃ and Carboxylated Multiwalled Carbon Nanotubes

Cited by 8 publications

References 30 publications

Effect of Interfacial Molecular Orientation on Power Conversion Efficiency of Perovskite Solar Cells

Effect of Interfacial Molecular Orientation on Power Conversion Efficiency of Perovskite Solar Cells

Accepting Excited High-Energy-Level Electrons and Catalyzing H₂ Evolution of Dual-Functional Ag-TiO₂ Modifier for Promoting Visible-Light Photocatalytic Activities of Nanosized Oxides

A Combined Theoretical and Experimental Study of CH₃NH₃PbI₃ Containing AVAI Films Prepared via an Intramolecular Exchange Process

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Photochemically Driven Modulated Charge Transfer at Local Contacts between CH3NH3PbI3 and Carboxylated Multiwalled Carbon Nanotubes

Cited by 8 publications

References 30 publications

Effect of Interfacial Molecular Orientation on Power Conversion Efficiency of Perovskite Solar Cells

Effect of Interfacial Molecular Orientation on Power Conversion Efficiency of Perovskite Solar Cells

Accepting Excited High-Energy-Level Electrons and Catalyzing H2 Evolution of Dual-Functional Ag-TiO2 Modifier for Promoting Visible-Light Photocatalytic Activities of Nanosized Oxides

A Combined Theoretical and Experimental Study of CH3NH3PbI3 Containing AVAI Films Prepared via an Intramolecular Exchange Process

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Resources

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Photochemically Driven Modulated Charge Transfer at Local Contacts between CH₃NH₃PbI₃ and Carboxylated Multiwalled Carbon Nanotubes

Accepting Excited High-Energy-Level Electrons and Catalyzing H₂ Evolution of Dual-Functional Ag-TiO₂ Modifier for Promoting Visible-Light Photocatalytic Activities of Nanosized Oxides

A Combined Theoretical and Experimental Study of CH₃NH₃PbI₃ Containing AVAI Films Prepared via an Intramolecular Exchange Process