Impact of Nonfullerene Acceptor Core Structure on the Photophysics and Efficiency of Polymer Solar Cells

Alamoudi, Maha A.; Khan, Jafar Iqbal; Firdaus, Yuliar; Wang, Kai; Andrienko, Denis; Beaujuge, Pierre M.; Laquai, Frédéric

doi:10.1021/acsenergylett.8b00045

Cited by 48 publications

(47 citation statements)

References 45 publications

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“…[29] The calculation of exciton binding energy and reorganization energy was based on the B3LYP functional and the 6-31G(d) basis set, since B3LYP is one of the most widely used functional that has previously been shown to give results of molecular orbital levels, exciton and ionic states of NFAs that agree well with the measurements. [30][31][32][33][34] For example, the measured HOMO level and lowest-energy absorption peak of IT-IC are -5.51 eV and 1.75 eV, respectively, [6] as compared to -5.49 eV and 1.76 eV calculated using B3LYP. The exciton binding and reorganization energies of NFAs calculated using B3LYP are comparable with reported previously.…”

Section: Methodsmentioning

confidence: 86%

Energy Loss in Organic Photovoltaics: Nonfullerene Versus Fullerene Acceptors

Liu

Ding

et al. 2019

Phys. Rev. Applied

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The energy loss experienced by organic photovoltaics (OPVs) is the difference between the lowest photogenerated exciton energy of donor or acceptor and the open circuit energy. It sets a fundamental limit to the open circuit voltage and hence the efficiency of OPVs. This loss can be as large as 0.7 eV for fullerene acceptors, although non-fullerene acceptors (NFAs) reduce this to 0.6 eV. Here, we systematically quantify the relationship between charge transfer energy loss (Δ ), non-radiative recombination loss, exciton binding energy, and intra-and inter-molecular electron-phonon couplings. Density functional theory and comprehensive quantum mechanical modeling is used to associate molecular volume, effective conjugation length, and the nonbonding character of molecules to these several energy losses. Nonradiative recombination in donor/NFA heterojunctions is quantified by the charge transfer state emission quantum yield, and its Frank-Condon shift. Our analytical results are consistent with measurements where Δ is varied between 0 and 0.6 eV using a variety of fullerene derivatives and thiophene-based NFAs paired with donor molecules. Molecular design rules to decrease the energy loss in OPVs derived from our analysis are provided.at the donor-acceptor HJ is: [5] .(Heterojunctions employing fullerene derivatives usually suffer from a loss of > 0.7 eV.Alternatives to fullerene acceptors have therefore been sought to reduce while extending the absorption spectrum into the infrared. The development of nonfullerene acceptors (NFAs)with acceptor-donor-acceptor (a-d-a) or perylene diimide (PDI)-based molecular motifs give freedom to tune the molecular energetics, absorption spectra and thin film morphologies through

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Section: Methodsmentioning

confidence: 86%

Energy Loss in Organic Photovoltaics: Nonfullerene Versus Fullerene Acceptors

Liu

Ding

et al. 2019

Phys. Rev. Applied

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“…Also, the effect of the MW of the acceptor in all‐polymer solar cells has been reported to influence the PCE . However, it is noteworthy that, until now, only a handful of studies have comprehensively reported time‐resolved studies of the photophysical processes in polymer:NFA systems …”

Section: Introductionmentioning

confidence: 99%

“…[27] However, it is noteworthy that, until now, only a handful of studies have comprehensively reported time-resolved studies of the photophysical processes in polymer:NFA systems. [28] In this work, four P3HT batches with different MWs (17,34,64, and 111 kDa) were used. The highest PCE was achieved for the intermediate MW system P3HT34K:O-IDTBR (6.6%), whereas the PCE gradually decreased for higher MWs, such as P3HT111K (4.4%), and for lower MW P3HT17K (4.0%).…”

Section: Introductionmentioning

confidence: 99%

P3HT Molecular Weight Determines the Performance of P3HT:O‐IDTBR Solar Cells

et al. 2019

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Large‐scale production of organic solar modules requires low‐cost and reliable materials with reproducible batch‐to‐batch properties. In case of polymers, their (photo)physical properties depend strongly on the polymers’ molecular weight (MW). Herein, the impact of the MW of the donor polymer poly(3‐hexylthiophene) (P3HT) on the photophysics is studied in blends with a recently developed rhodanine‐endcapped indacenodithiophene nonfullerene acceptor (IDTBR), a bulk heterojunction (BHJ) system that potentially fulfills the aforementioned criteria for large‐scale production. It is found that the power conversion efficiency (PCE) increases when the weight‐average MW is increased from 17 kDa (PCE: 4.0%) to 34 kDa (PCE: 6.6%), whereas a further increase in MW leads to a reduced PCE of 4.4%. It is demonstrated that the charge generation efficiency, as estimated from time‐delayed collection field experiments, varies with the P3HT MW and is the reason for the differences in photocurrent and device performance. These findings provide insight into the fundamental photophysical reasons of the MW dependence of the PCE, which is taken into account when using polymer‐based nonfullerene acceptor blends in solar cell devices and modules.

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“…3 However, these acceptors suffer from some drawbacks such as limited light absorption in the visible region, high cost, instability of surface morphology in the blend lms, difficulty in synthesis and purication and limited energy level tunability. 4,5 To overcome these challenges, there has been lot of reports in the recent literature on the design of nonfullerene based acceptors 6,7 with broader absorption, readily tunable energy levels, and ease of synthesis and purication. 8,9 Solution processable, non-fullerene bulk heterojunction (BHJ) solar cells with power conversion efficiencies (PCEs) > 8% have recently been reported which indicate the potential of nonfullerene electron acceptors.…”

Section: Introductionmentioning

confidence: 99%