Performance, Morphology, and Charge Recombination Correlations in Ternary Squaraine Solar Cells

Chen, Yao; Yang, Lin; Wu, Jianglin; Wang, Gang; Huang, Wei; Melkonyan, Ferdinand S.; Lu, Zhiyun; Huang, Yan; Marks, Tobin J.; Facchetti, Antonio

doi:10.1021/acs.chemmater.8b02746

Cited by 23 publications

(15 citation statements)

References 69 publications

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“…[31] Ideally, α = 1, signifies that carriers are swept out before recombination at short-circuit, indicating that bimolecular recombination is absent. [33] The α values are 0.96 and 0.94 for TPD-3:Y6 and TPD-3F:Y6 OSCs, respectively, implying greater bimolecular recombination in the latter cells (Figure 7a). Furthermore, the dependence of the V oc on P light , given by the relation V oc = n (k B T/e) ln(P light ) + C (n = ideality constant) was investigated to elucidate the effect of other recombination processes.…”

Section: Comparative Exciton Dissociation Charge Recombination and Charge Transportmentioning

confidence: 98%

To Fluorinate or Not to Fluorinate in Organic Solar Cells: Achieving a Higher PCE of 15.2% when the Donor Polymer is Halogen‐Free

Liao²,

Chen

et al. 2021

Advanced Energy Materials

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have received broad research attention as promising candidates for renewableenergy conversion devices owing to their mechanical flexibility, lightweight, absence of toxic heavy metals, and the potential for large-scale fabrication by roll-to-roll printing methodologies. [1] Realization of high-performance BHJ-OSCs devices has relied on photoactive materials design, synthesis, and characterization, as well as thin-film processing advances and device architecture optimization. [2] Since nonfullerene acceptors (NFAs) have now surpassed fullerene acceptors in key properties affecting OSC performance, including strong optical absorption in the visible-near-infrared (vis-NIR) region, adjustable energy levels, charge transport magnitude, and facile structural modification, considerable efforts have been devoted to understanding and perfecting NFAs in recent years. [3] The development of narrow-bandgap (NBG) NFAs with strong optical oscillator strength in the vis-NIR range of 600-1000 nm has been pioneered by several groups; specifically Hou and co-workers reported ITIC-4F [4] and IEICO-4F, [5] and Zhou and co-workers developed Y6. [6] These NFAs when combined with the proper donor polymers have enabled power conversion efficiencies (PCEs) ≈18% for both single-junction and multijunction devices, [7] Fluorination of the donor and/or acceptor blocks of photoactive semiconducting polymers is a leading strategy to enhance organic solar cell (OSC) performance. Here, the effects are investigated in OSCs using fluorine-free (TPD-3) and fluorinated (TPD-3F) donor polymers, paired with the nonfullerene acceptor Y6. Interestingly and unexpectedly, fluorination negatively affects performance, and fluorine-free TPD-3:Y6 OSCs exhibit a far higher power conversion efficiency (PCE = 14.5%) than in the fluorine-containing TPD-3F:Y6 blends (PCE = 11.5%). Transmission electron microscopy (TEM) analysis indicates that the TPD-3F:Y6 blends have larger phase domain sizes than TPD-3:Y6, which reduces exciton dissociation efficiency to 81% for TPD-3F:Y6 versus 93% for TPD-3:Y6. Additionally, grazing incidence wideangle X-ray scattering (GIWAXS) reveals that the TPD-3F:Y6 blends are less textured than those of TPD-3:Y6, while space-charge limited currents reveal lower and unbalanced hole/electron mobility in TPD-3F:Y6 versus TPD-3:Y6 blends. Charge recombination dynamic, transient absorption, and donoracceptor miscibility assays additionally support this picture. Furthermore, conventional architecture TPD-3:Y6 OSCs deliver a PCE of 15.2%, among the highest to date for halogen-free polymer donor OSCs. Finally, a large-area (20.4 cm 2 ) TPD-3:Y6 blend module exhibits an outstanding PCE of 9.31%, one of the highest to date for modules of area >20 cm 2 .

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Section: Comparative Exciton Dissociation Charge Recombination and Charge Transportmentioning

confidence: 98%

To Fluorinate or Not to Fluorinate in Organic Solar Cells: Achieving a Higher PCE of 15.2% when the Donor Polymer is Halogen‐Free

Liao²,

Chen

et al. 2021

Advanced Energy Materials

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“…In this regard, the squaraine derivative can be considered a potential alternative red and near-IR sensitizer − because of its high extinction coefficients in the region of 600–800 nm and its easy synthetic tunability. However, until recently, squaraine dyes have been relatively rarely used in photocatalysis, although the applications of squaraine dyes are as extensive as other visible light active antenna in the field of dye-sensitized solar cells − ,− and organic solar cells. − This limited utilization is thought to be derived from weaknesses such as the low structural stability of the central cyclobutene ring to nucleophilic attack, lack of directionality in the excited state with a fluorescent lifetime (∼1 ns), and formation of nonfluorescent aggregates, which limit the use of squaraine dyes in photocatalysis.…”

Section: Introductionmentioning

confidence: 99%

Utility of Squaraine Dyes for Dye-Sensitized Photocatalysis on Water or Carbon Dioxide Reduction

Choi

et al. 2019

ACS Omega

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Red light-sensitized squaraine (SQ) dyes were developed and incorporated into dye-sensitized catalysts (DSCs) with the formula of SQ/TiO2/Cat, and their efficacies were evaluated in terms of performance on either water or carbon dioxide reduction. Pt nanoparticles or fac-[Re(4,4′-bis-(diethoxyphosphorylmethyl)-2,2′-bipyridine)(CO)3Cl] were used as each catalytic center within the DSC frame of SQ/TiO2/Pt (Type I) or SQ/TiO2/Re(I) (Type II). In order to convey the potential utility of SQ in low energy sensitization, the following catalytic reductions were carried out under selective lower energy irradiation (>500 nm). Type I and II showed different catalytic performances, primarily due to the choice of solvent for each catalytic condition: hydrogenation was carried out in H2O, but CO2 reduction in dimethylformamide (DMF), and SQ was more stable in aqueous acid conditions for hydrogen generation than CO2 reduction in DMF. A suspension of Type I in 3 mL water containing 0.1 M ascorbic acid (pH = 2.66) resulted in efficient photocatalytic hydrogen evolution, producing 37 μmol of H2 for 4 h. However, in photocatalysis of Type II (SQ/TiO2/Re(I)) in 3 mL DMF containing 0.1 M 1,3-dimethyl-2-phenyl-1,3-dihydrobenzimidazole, the TiO2-bound SQ dyes were not capable of working as a low energy sensitizer because SQ was susceptible to dye decomposition in nucleophilic DMF conditions, resulting in DSC deactivation for the CO2 reduction. Even with the limitation of solvent, the DSC conditions for the utility of SQ have been established: the anchoring group effect of SQ with either phosphonic acid or carboxylic acid onto the TiO2 surface; energy alignment of SQ with the flat band potentials (Efb) of TiO2 semiconductors and the reduction power of electron donors; and the wavelength range of the light source used, particularly when >500 nm.

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“…reported a solution‐processed ternary BHJ‐OSC based on the SQ64:SQ48:PC 71 BM blend with a weight composition ratio 0.15:1:3, which exhibited a more encouraging PCE of 7.07% due to balanced mobilities and enhanced absorption. [ 87 ]…”

Section: Squaraine‐based Functional Materials For Photovoltaic Applicmentioning

confidence: 99%

Squaraine Dyes for Photovoltaic and Biomedical Applications

Sun

et al. 2020

Adv Funct Materials

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Squaraine dyes (SQs) are an important class of polymethine dyes with a unique reasonable‐stabilized zwitterionic structure, in which electrons are highly delocalized over the conjugated bridge. These dyes can not only be easily synthesized via a condensation, but also exhibit intense absorption and emission in the visible and near‐infrared region with excellent photochemical stability, making them attractive material candidates for many photoelectric and biomedical applications. Thus, in this review, after an introduction of SQs, the recent advances of SQs in the photovoltaic field are comprehensively summarized including dye‐sensitized solar cells, organic solar cells, and perovskite solar cells. Then, the important advances in the use of SQs as the biosensors, biological imaging, and photodynamic/photothermal therapy reagents in the biomedical field are also discussed. Finally, a summary and outlook will be provided with some new perspectives for the future design of SQs.

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Performance, Morphology, and Charge Recombination Correlations in Ternary Squaraine Solar Cells

Cited by 23 publications

References 69 publications

To Fluorinate or Not to Fluorinate in Organic Solar Cells: Achieving a Higher PCE of 15.2% when the Donor Polymer is Halogen‐Free

To Fluorinate or Not to Fluorinate in Organic Solar Cells: Achieving a Higher PCE of 15.2% when the Donor Polymer is Halogen‐Free

Utility of Squaraine Dyes for Dye-Sensitized Photocatalysis on Water or Carbon Dioxide Reduction

Squaraine Dyes for Photovoltaic and Biomedical Applications

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