Vibrational Sum Frequency Generation Spectroscopy of Fullerene at Dielectric Interfaces

Sohrabpour, Zahra; Kearns, Patrick; Massari, Aaron M.

doi:10.1021/acs.jpcc.5b10918

Cited by 18 publications

(24 citation statements)

References 56 publications

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“…SFG has been applied to study polythiophene molecular orientations at interfaces. ,− Here, we focused on elucidation of molecular structures at the buried polythiophene/graphene interfaces, and the correlations between the PT side-chain length and the molecular orientation of the PT thiophene backbone at such interfaces using SFG. We compared the interfacial thiophene backbone orientations at the PT/graphene interfaces to those at the PT/CaF 2 interfaces, as well as the PT/perovskite interfaces that were reported previously .…”

Section: Introductionmentioning

confidence: 99%

Molecular Orientations at Buried Conducting Polymer/Graphene Interfaces

Guo

et al. 2021

Macromolecules

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Graphene and semiconducting polymers have been extensively researched for use in many microelectronic devices. For both devices with layered structures and graphene–semiconducting polymer composite materials, molecular interactions between graphene and semiconducting polymers play significant roles in determining the interfacial properties and impact the device performance. In this research, molecular orientations of polymer backbones of three polythiophenes (PTs) with different side-chain lengths at the buried PT/graphene interfaces were determined using sum frequency generation (SFG) vibrational spectroscopy. It was found that the longer the PT side chain, the larger the PT backbone tilt angle measured. Therefore, the PT backbone with a longer side-chain length adopts a more lying-down pose on graphene. The same trend for orientation tilt angles of PTs with different side-chain lengths at PT/CaF2 interfaces was observed. When comparing the same PT backbone orientation, PT at the PT/graphene interface generally lies down more compared to that at the PT/CaF2 interface, due to stronger π–π interactions between the PT backbone conjugated rings and graphene. The different PT backbone orientations at interfaces are likely caused by varied interactions between the PT backbone and the substrate and between side chains and the substrate, as well as intermolecular and intramolecular interactions between PT molecules (including side chains and backbones). The determination of PT backbone orientations at buried interfaces helps to understand molecular interactions at these interfaces, aiding in the design of polymer/graphene interfaces with optimal structure and improved properties.

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Section: Introductionmentioning

confidence: 99%

Molecular Orientations at Buried Conducting Polymer/Graphene Interfaces

Guo

et al. 2021

Macromolecules

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“…Resolving the molecular orientation of such functional groups is achieved by controlling the polarization of each incoming beam as well as the generated SFG beam. Recent progress in SFG research has shown that SFG is a powerful tool to investigate surfaces and interfaces of many systems such as biological systems, − organic molecules, , and water surface/interfaces ,− as well as organic semiconductor materials. − The research reported in this article aims to understand the correlation between the structure of polythiophene (PT) at the buried perovskite/polythiophene (PT) interface in a solar cell and the solar cell efficiency.…”

Section: Introductionmentioning

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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“…Sohrabpour et al showed that SFG can also be used to study fullerene thin films on dielectric substrates. Fullerene is one of the most commonly used acceptor materials in OPV devices, and SFG has been able to study fullerene interfacial structures, which proved SFG has the capability to study not only donor materials but also acceptor materials . SFG study on electronic structures at buried interfaces also demonstrated that SFG is a powerful interface sensitive tool that can be used to study these structures in organic semiconductors, as reported by Li et al As stated before, most progress still focuses on OFETs so far, but these two studies have demonstrated that SFG can have a broader impact in elucidating interfacial properties in OPVs and OLEDs devices in situ.…”

Section: Applications Of Sfg To Study Polymer Surfaces and Interfacesmentioning

confidence: 83%

Studying Polymer Surfaces and Interfaces with Sum Frequency Generation Vibrational Spectroscopy

et al. 2016

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Vibrational Sum Frequency Generation Spectroscopy of Fullerene at Dielectric Interfaces

Cited by 18 publications

References 56 publications

Molecular Orientations at Buried Conducting Polymer/Graphene Interfaces

Molecular Orientations at Buried Conducting Polymer/Graphene Interfaces

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

Studying Polymer Surfaces and Interfaces with Sum Frequency Generation Vibrational Spectroscopy

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