Modeling Spontaneous Charge Transfer at Metal/Organic Hybrid Heterostructures

Abstract

Hybrid materials are crucial in photovoltaics where the overall efficiency of the heterostructure is closely related to the level of charge transfer at the interface. Here, using various metal / poly(3hexylthiophene)(P3HT) heterostructure models, we reveal that the level of spontaneous charge transfer and electronic coupling at these interfaces depend on the conformational regularity of the organic polymer deposited on the metal substrate. Using ab-initio quantum chemical calculations based on density functional theory (DFT) and heterodyne vibrational sum frequency generation (HD-VSFG) measurements, we show that inducing regio-randomness into the organic polymer modifies the intensity of interfacial electronic states, level of hybridization, density of interfacial charge transfer and the electronic wave function of the material. We present the HD-VSFG responses of the metal/P3HT heterojunctions containing both regio-regular and regio-random P3HT structures and show that the amount of non-resonant signal is closely related to the level of the spontaneous charge transfer at the interface. Thus, by measuring the non-resonant response of the metal/P3HT heterojunctions, the level of spontaneous charge transfer at the interface can be determined. arXiv:1908.06269v1 [cond-mat.mtrl-sci]

Charge Transfer Dynamics in Organic–Inorganic Hybrid Heterostructures—Insights by Vibrational‐Sum Frequency Generation Spectroscopy

“…Furthermore, Özçelik et al combined DFT calculations with HD-VSFG measurements and obtained information about the interplay between molecular ordering/orientation and interfacial charge transfer. [52] It was observed that an increase in the regio-randomness (geometrical regio-randomness was intro- duced when the alkyl side chains were attached to the back bone from random locations in alternating monomers) of P3HT translates into an inefficient interlayer charge transfer, which is evident from the HD-VSFG measurements by correlating the intensity of the non-resonant contribution with the level of charge transfer. [52] These studies underline the potential of HD-VSFG to yield insights into function-determining processes in materials for efficient photovoltaic systems.…”

Ladungstransferdynamiken in organisch–anorganischen hybriden Heterostrukturen – Einblicke mithilfe von Summenfrequenzspektroskopie

“…Dies ist aus den HD-SFS-Messungen ersichtlich, indem die Intensität des NR Beitrags mit dem Grad des Ladungstransfers korreliert wird. [52] Die vorgestellten Studien unterstreichen das Potenzial von HD-SFS, Einblicke in funktionsbestimmende Prozesse in Materialien für effiziente Photovoltaiksysteme zu gewinnen. Sie konzentrierten sich auf Veränderungen beim Ladungstransfer zwischen Goldsubstraten und P3HT-Adsorbaten in Abhängigkeit von der Polarisation des Anregungspulses.…”

“…Des Weiteren kombinierten Özçelik et al DFT-Berechnungen mit HD-SFS-Messungen und erhielten Informationen über das Zusammenspiel zwischen molekularer Ordnung/Orientierung und Ladungstransfer an der Grenzfläche. [52] Es wurde beobachtet, dass eine Zunahme von nicht regioregularen Bereichen (diese geometrischen Bereiche wurden eingeführt, als die Alkylseitenketten an zufälligen Stellen der alternierenden Monomere an das Rückgrat angebracht wurden) von P3HT zu einem ineffizienten Ladungstransfer zwischen den Schichten führt. Dies ist aus den HD-SFS-Messungen ersichtlich, indem die Intensität des NR Beitrags mit dem Grad des Ladungstransfers korreliert wird.…”

Structural and energetic properties of P3HT and PCBM layers on the Ag(1 1 1) surface

“…Hybrid heterostructures involving organic material thin films on inorganic substrates demonstrate unique properties which are radically different from their isolated components [1,2]. For appropriately chosen materials, the interfacial electrical, magnetic and optical properties can be engineered to realize new device functionalities, with many applications in organic electronics including light-emitting diodes, field-effect transistors, and solar cells [3][4][5][6].…”