Atomistic Insight Into Donor/Acceptor Interfaces in High‐Efficiency Nonfullerene Organic Solar Cells

Han, Guangchao; Guo, Yuan; Ma, Xiaoyi; Yi, Yuanping

doi:10.1002/solr.201800190

Cited by 49 publications

(58 citation statements)

References 77 publications

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“…However, it is not possible to unequivocally assign features at 2.2 nm to either donor or acceptor. This distance roughly corresponds to the PBDB-T (100) spacing 20,29 as well as to possible backbone-to-backbone distances of ITIC 16,17 as shown in Fig. 2 and 3.…”

Section: Impact Of Additives and Thermal Annealing On Molecular Orienmentioning

confidence: 62%

“…22,[35][36][37] Han and co-workers performed atomistic simulations of the PBDB-T: ITIC interface blend. 17 They predicted that the combination of using the additive DIO and thermal annealing favours a docking of the IC moieties to the electron withdrawing BDD unit of the polymer. Thus, thermal annealing under the use of DIO or CN induces the nucleation of ITIC crystals at PBDB-T.…”

Section: Impact Of Additives and Thermal Annealing On Molecular Orienmentioning

confidence: 99%

“…16 We infer that an ITIC polymorph with chain-like conformation is present after thermal annealing, favouring docking to PBDB-T by arrangement of the electron withdrawing groups of both molecules at the interface. 17 This ITIC reorganization leads to higher shortcircuit current densities. Our results suggest that optimal p-orbital overlapping is crucial for charge-carrier generation.…”

Section: Introductionmentioning

confidence: 99%

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Visualizing morphological principles for efficient photocurrent generation in organic non-fullerene acceptor blends

Köntges

Perkhun

Kammerer

et al. 2020

Energy Environ. Sci.

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Section: Impact Of Additives and Thermal Annealing On Molecular Orienmentioning

confidence: 62%

Section: Impact Of Additives and Thermal Annealing On Molecular Orienmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Visualizing morphological principles for efficient photocurrent generation in organic non-fullerene acceptor blends

Köntges

Perkhun

Kammerer

et al. 2020

Energy Environ. Sci.

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“…This preferential ordering can be ascribed to the torsion of the thiophenes (in the 2-(2-ethylhexyl)thiophene side chains) with respect to the D moieties of the PBDB-T backbones ( Figure S7A), which hinders a close contact with the A moieties of the IT-OM backbones. 32 However, the branched alkyl side chains can also prevent stacking between PBDB-T and IT-OM. The difference is that, while the branched alkyl side chains are attached on both sides of the PBDB-T-D moieties, they are attached on only one side of the PBDB-T-A moieties, which leaves the other side quite open for interaction with IT-OM-A ( Figure S7B).…”

Section: Pbdb-t/it-om Packing Pattern In the Blendsmentioning

confidence: 99%

Organic Solar Cells Based on Non-fullerene Small-Molecule Acceptors: Impact of Substituent Position

Wang

Brédas

2020

Matter

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Molecular engineering of non-fullerene small-molecule acceptors (SMAs) plays a key role in enhancing the performance of organic solar cells. An effective strategy is to introduce functional groups into SMA end groups to tune the electronic and morphological properties of polymer/SMA blends. Here, molecular dynamics simulations and long-range corrected density functional theory calculations are combined to examine the impact of the position of methoxy substitution in the SMA end groups. As representative systems, blends of the IT-OM small-molecule acceptor with the PBDB-T polymer donor are explored; three different positions of the methoxy substitution of the IT-OM end groups are examined. By considering intermolecular mixing and packing, the energetic distribution of the charge-transfer electronic states, the exciton-dissociation and non-radiative recombination processes, and the electron-transfer rates among adjacent acceptors, we provide a comprehensive molecular-scale rationalization of the significant experimental variations in device performance for PBDB-T/IT-OM-based solar cells as a function of methoxy position.

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“…Significantly, the docking of acceptor (whether fullerene or NF acceptor) with the terminal groups (where the distribution of LUMO is higher than that of HOMO) of an A‐π‐D‐π‐A small‐molecule donor can result in weak V CR and

E_{b, C T}

but moderate V ED , which can simultaneously suppress NR CT recombination and ensure efficient exciton dissociation. It is worth to note that for NF OSCs based on D‐A copolymer donors and small‐molecule A‐π‐A acceptors, the docking of the terminal A groups of small‐molecule acceptors with the A unit of copolymer donors would be the ideal interfacial arrangements …”

Section: Theoretical Description Of Electronic Processes In Organic Smentioning

confidence: 99%

Origin of Photocurrent and Voltage Losses in Organic Solar Cells

Han

2019

Advcd Theory and Sims

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Organic solar cells (OSCs) have recently achieved power conversion efficiencies (PCEs) of over 16%. However, there still exist large losses in photocurrent and/or voltage in state-of-the-art OSCs, making the PCEs still far below those of inorganic counterparts. Here, the factors and electronic processes for photocurrent and voltage losses are identified and discussed in the framework of device physics and photophysics. To simultaneously obtain both high photocurrent density and low voltage loss toward 20% PCEs, it is crucial to suppress the non-radiative (NR) recombination of the lowest charge-transfer (CT) state at the donor-acceptor interface. In principle, theoretical simulations can provide molecular insight into the origin of these losses, which is essential to guide material design. In particular, the authors highlight the importance of the local interface morphologies and the vibronic couplings on suppressing the NR decay of the lowest CT state according to recent theoretical studies. (1 of 17)www.advancedsciencenews.com www.advtheorysimul.com as A, has achieved a high J SC of 25 mA cm −2 . [5] Nevertheless, the value of J SC /J SC,SQ for the E g of 1.33 eV is only 0.71, implying that even in the best OSCs, the photocurrent loss is still non-negligible. Now we turn to the loss in open-circuit voltage. The voltage loss ( V OC ) or energy loss (E los s , i.e., q V OC ) is defined asEven in the ideal SQ limit, the V OC is inevitable. [9] The V OC can be as low as 0.3 V in GaAs and slightly higher (0.4-0.55 V) in c-Si and perovskite solar cells, while the V OC in high-efficiency OSCs is usually around 0.6 V or larger. [10] For example, the best fullerene-based OSCs based on PffBT4T-C 9 C 13 :PC 71 BM have a large V OC of 0.87 V for an E g of 1.65 eV, despite of a high J SC /J SC,SQ value of 0.82. [11] In order to improve the PCE for a given E g , it is important to minimize V OC without sacrificing the generation of photocurrent. [12,13] Here, the PCE versus E g and V OC is calculated by Equations (1), (3), and (6), based on two reliable assumptions: i) the E QE P V is set to a fixed value of 85% when E ≥ E g , even though the highest value has reached 90%, [14] because it is very difficult to obtain the maximum value over the whole range in real systems, and ii) the FF is set to 80%, since the highest FF of 80.79% has been reported, [15] which is comparable to those of c-Si and GaAs solar cells (80-86%). [8] Hence, a low V OC of, for example, 0.45 V can produce PCEs over 20% at a wide E g range of 1.1-1.6 eV (Figure 1b). This suggests that a PCE of 20% should be a reasonable target for single-junction OSCs, providing a large area to explore in the future. To achieve this target, as a preliminary step, the origin of photocurrent and voltage losses in OSCs must be identified.In the following, we first describe the optical and electronic processes in OSCs and especially, point out the adverse factors or processes that can result in the photocurrent loss. Second, we

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Atomistic Insight Into Donor/Acceptor Interfaces in High‐Efficiency Nonfullerene Organic Solar Cells

Cited by 49 publications

References 77 publications

Visualizing morphological principles for efficient photocurrent generation in organic non-fullerene acceptor blends

Visualizing morphological principles for efficient photocurrent generation in organic non-fullerene acceptor blends

Organic Solar Cells Based on Non-fullerene Small-Molecule Acceptors: Impact of Substituent Position

Origin of Photocurrent and Voltage Losses in Organic Solar Cells

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