Photoinduced intra- and inter-molecular charge transfer dynamics in organic small molecules with an intra-molecular push–pull electronic structure

Ji, Yang; Xu, Lingxia; Mu, Xinyu; Wang, Wenjing; Gao, Kun

doi:10.1039/d2tc01534j

Cited by 6 publications

(5 citation statements)

References 38 publications

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“…In the solid state, the two acceptors exhibit broadened and redshifted absorption with 𝜆 max film at 777 and 764 nm for 3TTS-4F and 3TTB-4F, respectively. These different redshifts (51 and 38 nm) may be attributed to the different degrees of intermolecular charge transfer (CT)-mediated coupling, [40,41] which is closely related to the packing modes. Based on the optical absorption onset (𝜆 onset film ) in the solid state, the optical bandgaps (E g opt ) of 3TTS-4F and 3TTB-4F were estimated to be 1.41 and 1.46 eV, respectively.…”

Section: Resultsmentioning

confidence: 99%

Simple‐Structured Acceptor with Highly Interconnected Electron‐Transport Pathway Enables High‐Efficiency Organic Solar Cells

Gu,

Zeng,

et al. 2024

Advanced Materials

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Achieving desirable charge‐transport highway is of vital importance for high‐performance organic solar cells (OSCs). Here, we show how molecular packing arrangements can be regulated via tuning the alkyl‐chain topology, thus resulting in a three‐dimensional network stacking and highly interconnected pathway for electron transport in a simple‐structured nonfused‐ring electron acceptor (NFREA) with branched alkyl side‐chains. As a result, a record‐breaking power conversion efficiency of 17.38% (certificated 16.59%) is achieved for NFREA‐based devices, thus providing an opportunity for constructing low‐cost and high‐efficiency OSCs.This article is protected by copyright. All rights reserved

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Section: Resultsmentioning

confidence: 99%

Simple‐Structured Acceptor with Highly Interconnected Electron‐Transport Pathway Enables High‐Efficiency Organic Solar Cells

Gu,

Zeng,

et al. 2024

Advanced Materials

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“…Using the electron-withdrawing and electron-donating units layer presents a general rule to design high delocalization energy and dipole non-fullerene molecular structures for developing OSCs. ,− Within the LBL structure, we can expect that the purely compactly stacked Y6 molecules become negatively and positively charged in the non-fullerene Y6 layer structures under photoexcitation through intramolecular charge transfer. We should note that one Y6 molecule has four electrical dipoles with opposite directions under photoexcitation. − However, the four electrical dipoles are normally not symmetrically placed within Y6 molecules when mixing with donor PM6 to form PM6:Y6 BHJ in both vertical and lateral directions in the ITO/PEDOT:PSS/PM6:Y6/PDIN/Al device, as illustrated in Figure a. As a result, we can hypothesize that a photoexcitation can generate superimposed and oriented electrical dipoles within pure compactly stacked Y6 molecules due to one Y6 molecule with electron-withdrawing and electron-donating structures.…”

Section: Resultsmentioning

confidence: 99%

Enhanced Self-Stimulated Dissociation in Non-fullerene Layer-by-Layer Organic Solar Cells through Superimposed and Oriented Dipolar Polarization

Huang

Xie

et al. 2023

J. Phys. Chem. C

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A non-fullerene layer-by-layer (LBL) structure can establish effective donor/acceptor (D/A) interfaces and lead to remarkable photovoltaic efficiencies based on facile solution processing properties, as compared with nonfullerene bulk heterojunction devices. However, the operating mechanisms have been remaining as an unaddressed issue to understand the role of D/A interfaces toward developing photovoltaic processes in non-fullerene LBL where the high electrically polarizable non-fullerene molecules exist. Here, we address the operating mechanisms of photovoltaic actions by in situ monitoring the dynamic D/A interfaces upon selectively exciting the non-fullerene acceptor layer to address the effects of optically induced superimposed and oriented dipoles on electron−hole pair self-stimulated dissociation in non-fullerene LBL organic solar cells [ITO/PEDOT:PSS/PM6/Y6/PDIN/Al]. Essentially, the self-stimulated dissociation at the D/A interfaces can be monitored by magneto-photocurrent while separately exciting the donor and acceptor components with two different laser beams. We observed an interesting phenomenon that optically exciting the non-fullerene Y6 acceptor component leads to easier electron−hole dissociation at D/A interfaces and consequently an increase on electron−hole pair self-stimulated dissociation to generate photocurrent in non-fullerene LBL solar cells. This phenomenon presents a hypothesis that optically exciting the compactly stacked non-fullerene Y6 molecules induces superimposed and oriented electrical dipoles within A−D−A−D−A structures to increase the self-stimulated dissociation at D/A interfaces toward developing the photovoltaic actions in non-fullerene LBL solar cells. This hypothesis is supported by our photoinduced capacitance result: photoexcitation increases bulk polarization in the dipolar polarization zone in non-fullerene LBL solar cells. Furthermore, optically generated dipoles are verified by photoinduced magnetocapacitance, solely generated by photoinduced polarization rather than photogenerated carriers, in non-fullerene LBL PM6/Y6. Clearly, the optically generating superimposed and oriented electrical dipoles become a critical parameter to operate the photovoltaic actions at D/A interfaces in non-fullerene LBL solar cells.

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“…With the rapid development of NFA molecules in applications of OSCs, different theoretical models and methods have been used to study their unique excited state and charge characteristics. [21,24,26,42,43] For instance, by density functional theory (DFT) and time-dependent DFT (TD-DFT) methods, Cui et al systematically investigated the structure-property relationship and excited-state CT characteristics based on two types of NFA molecules. [42] In addition, Zhu et al investigated the effect of different intermolecular aggregations on the exciton binding energy in NFA molecules by a self-consistent quantum mechanics/embedded charge approach.…”

Section: Methodsmentioning

confidence: 99%

“…[21] Recently, by emphasizing the intramolecular push-pull electronic structure and intermolecular aggregation of typical NFA molecules, we theoretically proposed a universal synergistic charge transfer model incorporating both the intra-and intermolecular pathways. [24,43] In this work, to clarify the effect of the NFA molecular push-pull electronic structure on the interfacial charge dynamics, we further construct an organic D/A interface composed of a polymer donor and a NFA molecule (see Figure 1a), where the quasi-1D-conjugated skeleton of the two molecules and the intramolecular push-pull electronic structure of NFA molecule are emphasized. The molecular chain with sites 1-92 represents a polymer donor and the chain with sites 93-128 an NFA molecule.…”

Section: Methodsmentioning

confidence: 99%

Effect of the Push–Pull Electronic Structure of Nonfullerene Acceptor Molecules on the Interfacial Charge Dynamics in Heterojunction Organic Solar Cells

et al. 2022

Adv Energy and Sustain Res

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Benefitting from the development of nonfullerene acceptors (NFAs), the power conversion efficiency (PCE) approaching 19% has been achieved in single-junction organic solar cells (OSCs). [1,2] Compared with fullerene acceptors (FAs), NFAs present different aspects of advantages, such as the tunable energy levels, [3,4] strong absorption in the visible-to-near-infrared wavelength range, [5,6] and various molecular aggregation structures. [7,8] Despite molecular diversity, most of the highperformance NFA molecules (e.g., ITIC and Y6) have push-pull electronic structure, where the central group has stronger electron push ability, the terminal groups have stronger electron pull ability, and sometimes π-bridges connecting the central group and the terminal groups. [9,10] Up to now, different strategies have been explored to strengthen the electron push ability of the central group, such as extending the conjugation length, [11,12] introducing strong electron push group (e.g., alkoxy or alkyl amino side groups), [13,14] and inserting quinone resonance structure. [15] To strengthen the electron pull ability of the terminal groups, one usually introduces halogen atoms (e.g., fluorine and chlorine). [16][17][18][19] The push-pull electronic structure of NFA molecules can result in their intramolecular charge transfer character, reducing the binding energy of their excited states. [20][21][22][23] Recent works have successively reported that the excited states in NFA molecules might behave in intra-and intermolecular charge transfer (CT) states, [24,25] which can dissociate into free charges even at room temperature without the assistance of a donor/acceptor (D/A) energy offset. [24][25][26] In FA-based OSCs, we know that polymer donors usually act as the light-absorbing components due to the poor absorption of FA molecules, [27] such that charges mainly originate from the donor excitation via experiencing the interfacial electron transfer into FA molecules. [28] In NFA-based OSCs, polymer donors and NFA molecules usually have complementary absorption; thus, charge generation presents diverse channels. When the donor molecule is photoexcited, the excited electron transfers into NFA molecule. [20,22,23] When NFA molecule is photoexcited, the excited hole transfers into donor molecule. [10,21,25] Recently, a third charge generation channel was revealed in

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Photoinduced intra- and inter-molecular charge transfer dynamics in organic small molecules with an intra-molecular push–pull electronic structure

Abstract: As electron acceptor materials, organic small molecules with intra-molecular push-pull electronic structure have been widely used in high-efficient organic solar cells (OSCs), usually referred to as non-fullerene acceptor (NFA) molecules....

Cited by 6 publications

References 38 publications

Simple‐Structured Acceptor with Highly Interconnected Electron‐Transport Pathway Enables High‐Efficiency Organic Solar Cells

Simple‐Structured Acceptor with Highly Interconnected Electron‐Transport Pathway Enables High‐Efficiency Organic Solar Cells

Enhanced Self-Stimulated Dissociation in Non-fullerene Layer-by-Layer Organic Solar Cells through Superimposed and Oriented Dipolar Polarization

Effect of the Push–Pull Electronic Structure of Nonfullerene Acceptor Molecules on the Interfacial Charge Dynamics in Heterojunction Organic Solar Cells

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