Ultrafast electron and hole transfer in bulk heterojunctions of low-bandgap polymers

Kozlov, Oleg V.; Pavelyev, V.G.; Gier, Hilde D. de; Havenith, Remco W. A.; Loosdrecht, P. H. M. van; Hummelen, Jan C.; Pshenichnikov, Maxim S.

doi:10.1515/oph-2016-0003

Cited by 7 publications

(8 citation statements)

References 56 publications

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“…[38][39][44][45][46] Controlled polymer aggregation in thin films has been shown to directly impact the morphology and performance of polymer-fullerene solar cells, while the relationship has hardly been explored in APSCs. [9,16,[47][48][49][50][51][52] As the molecular weight is varied, many photovoltaic polymers exhibit a change in solution/thin film aggregation tendencies and, for films, texturing evident in optical, morphological, and thermal analysis. [9,33,43,45,50,[53][54][55][56][57][58][59] Representative donor-acceptor polymer pairs that have been investigated by varying the M n of at least one component are summarized in Scheme 1.…”

Section: Introductionmentioning

confidence: 99%

“…The current main focus in furthering the understanding of optimal APSC morphology is on how to control the phase separation and tune it for optimal OPV performance . Controlled polymer aggregation in thin films has been shown to directly impact the morphology and performance of polymer–fullerene solar cells, while the relationship has hardly been explored in APSCs . As the molecular weight is varied, many photovoltaic polymers exhibit a change in solution/thin film aggregation tendencies and, for films, texturing evident in optical, morphological, and thermal analysis .…”

Section: Introductionmentioning

confidence: 99%

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Photoactive Blend Morphology Engineering through Systematically Tuning Aggregation in All‐Polymer Solar Cells

Wang

Eastham

Aldrich

et al. 2018

Advanced Energy Materials

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Polymer aggregation plays a critical role in miscibility of materials and the performance of allpolymer solar cells (APSCs). However, many aspects of how polymer texturing and aggregation affect photoactive blend film microstructure and photovoltaic performance are poorly understood.Here we study the effects of aggregation in donor-acceptor blends in which the number-average molecular weights (M n s) of both an amorphous donor polymer poly [4,8-bis(5-(2ethylhexyl)This article is protected by copyright. All rights reserved.3 alt-5,5'-(2,2'-bithiophene)} (P(NDI2OD-T2)) are systematically varied. The photovoltaic performance is correlated with active layer microstructural and optoelectronic data acquired by indepth transmission electron microscopy (TEM), grazing incidence wide-angle X-ray scattering (GIWAXS), thermal analysis, and optical spectroscopic measurements. Coarse-grained modeling provides insight into the effects of polymer aggregation on the blend morphology. Notably, the computed average distance between the donor and the acceptor polymers correlates well with solar cell photovoltaic metrics such as short-circuit current density (J sc ) and represents a useful index for understanding/predicting active layer blend material intermixing trends. Importantly, these results demonstrate that for polymers with different texturing tendencies (amorphous/semicrystalline), key for optimal APSC performance, photovoltaic blend morphology can be controlled via both donor and acceptor polymer aggregation.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Photoactive Blend Morphology Engineering through Systematically Tuning Aggregation in All‐Polymer Solar Cells

Wang

Eastham

Aldrich

et al. 2018

Advanced Energy Materials

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“…To further improve the device efficiency, therefore, an understanding of the photophysical processes leading to CT is essential. − Due to the relatively low extinction coefficients of fullerenes in the solar spectral range, alternative CT pathways initiated by photoexcitation in the acceptor are often neglected. This concept has been challenged by several reports showing that low-donor-content devices (<10% weight ratio) can achieve similar or even higher-power-conversion efficiencies than higher-donor-content devices, ,− highlighting the importance of considering the mechanism of charge separation via the hole transfer pathway. Recently, several groups have reported the spectral dependence of charge generation yields when exciting the fullerene excitonic states in the ultraviolet and provided further evidence for the hole transfer pathway. ,− Armin and co-workers have used a two-diode model to successfully describe the internal quantum efficiency in the visible range and propose that the hole transfer pathway is independent of excitation wavelength.…”

mentioning

confidence: 99%

“…This concept has been challenged by several reports showing that low-donor-content devices (<10% weight ratio) can achieve similar or even higher-power-conversion efficiencies than higher-donor-content devices, ,− highlighting the importance of considering the mechanism of charge separation via the hole transfer pathway. Recently, several groups have reported the spectral dependence of charge generation yields when exciting the fullerene excitonic states in the ultraviolet and provided further evidence for the hole transfer pathway. ,− Armin and co-workers have used a two-diode model to successfully describe the internal quantum efficiency in the visible range and propose that the hole transfer pathway is independent of excitation wavelength. Recent work on OPVs employing nonfullerene acceptors have highlighted the potential for exploiting the hole transfer pathway. − Furthermore, Kandada and co-workers have reported that electron transfer following energy transfer from fullerene to the donor can also contribute to charge generation.…”

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confidence: 99%

Efficient Charge Generation via Hole Transfer in Dilute Organic Donor–Fullerene Blends

Song

Schubert

Liu

et al. 2020

J. Phys. Chem. Lett.

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Efficient organic photovoltaics (OPVs) require broadband charge photogeneration with near-unity quantum yield. This can only be achieved by exploiting all pathways that generate charge. Electron transfer from organic donors to acceptors has been well-studied and is considered the primary path to charge photogeneration in OPVs. In contrast, much less is known about the hole transfer pathway. Here we study charge photogeneration in an archetypical system comprising tetraphenyldibenzoperiflanthene:C70 blends using our recently developed multispectral twodimensional electronic spectroscopy (M-2DES), supported by time-dependent density functional theory and fully quantum-mechanical Fermi's golden rule rate calculations. Our approach identifies in real time two rapid charge transfer pathways that are confirmed through computational analysis. Surprisingly, we find that both electron and hole transfer occur with comparable rates and efficiencies, facilitated by donor-acceptor electronic interactions. Our results highlight the importance of the hole transfer pathway for optimizing the efficiency of OPV devices employing small-molecule heterojunctions.

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“…The hole‐transfer in PSCs with fullerenes and their derivatives as acceptors has been studied by utilizing time‐resolved photoluminescence (PL), quasi‐steady‐state photoinduced absorption, and ultrafast transient absorption (TA) spectra . It has been demonstrated in fullerene‐based PSCs that interfacial hole transfer is usually affected by weight concentration, phase separation, molecule morphology, and driving force .…”

Section: Introductionmentioning

confidence: 99%

Improved Charge Generation via Ultrafast Effective Hole‐Transfer in All‐Polymer Photovoltaic Blends with Large Highest Occupied Molecular Orbital (HOMO) Energy Offset and Proper Crystal Orientation

Jin

Yuan

Guo

et al. 2018

Adv Funct Materials

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Improved charge generation via fast and effective hole transfer in all-polymer solar cells (all-PSCs) with large highest occupied molecular orbital (HOMO) energy offset (ΔE H ) is revealed utilizing ultrafast transient absorption (TA)spectroscopy. Blending the same nonfullerene acceptor poly{[N,N′-bis(2octyldodecyl)-naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5,5′-(2,2′bithiophene) (N2200) with three different donor polymers produces all-polymer blends with different ΔE H . The selective excitation of N2200 component in blends enables to uncover the hole transfer process from hole polaron-induced bleaching and absorption signals probed at different wavelength. As the ΔE H is enhanced from 0.14 to 0.37 eV, the hole transfer rate rises more than one order and the hole transfer efficiency increases from 12.9% to 86.8%, in agreement with the trend of internal quantum efficiency in the infrared region where only N2200 has absorption. Additionally, Grazing-incidence wide-angle X-ray scattering measurements indicate that face-on crystal orientation in both polymer donor and acceptor also plays an important role in facilitating the charge generation via hole transfer in all-PSCs. Hence, large ΔE H and proper crystal orientation should be considered in material design for efficient hole transfer in N2200-based heterostructures. These results can provide valuable guidance for fabrication of all-PSCs to further improve power conversion efficiency.

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Ultrafast electron and hole transfer in bulk heterojunctions of low-bandgap polymers

Cited by 7 publications

References 56 publications

Photoactive Blend Morphology Engineering through Systematically Tuning Aggregation in All‐Polymer Solar Cells

Photoactive Blend Morphology Engineering through Systematically Tuning Aggregation in All‐Polymer Solar Cells

Efficient Charge Generation via Hole Transfer in Dilute Organic Donor–Fullerene Blends

Improved Charge Generation via Ultrafast Effective Hole‐Transfer in All‐Polymer Photovoltaic Blends with Large Highest Occupied Molecular Orbital (HOMO) Energy Offset and Proper Crystal Orientation

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