Impact of alkyl chain branching positions on molecular packing and electron transport of dimeric perylenediimide derivatives

Guo, Yuan; Han, Guangchao; Yi, Yuanping

doi:10.1016/j.jechem.2018.11.012

Cited by 21 publications

(22 citation statements)

References 68 publications

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“…Although the π–π stacking can be revealed by experimental techniques, such as X‐ray diffraction, it is still difficult to probe the molecular details of intermolecular orientations, coordination number, and local ordering in the disordered region of the active layer . MD simulations combined with electronic‐structure calculations, electron‐transfer theory, and KMC simulations would be useful to elucidate the thin‐film packing morphologies of the NF acceptors and the relationship between molecular packing structures and charge transport properties …”

Section: Theoretical Description Of Electronic Processes In Organic Smentioning

confidence: 99%

“…Importantly, the electron mobility of the bay‐linked dimeric PDI with linear alkyl chains is improved by nearly 20 times with respect to the monomeric PDI with branched alkyl chains, as a result of simultaneously enhanced intermolecular and intramolecular interactions. Based on the bay‐linked dimeric PDIs, the impact of branching positions of the alkyl substituents was also investigated . As the branching position moves away from the PDI backbone, the short contacts between the PDI units are first enhanced and then reduced.…”

Section: Theoretical Description Of Electronic Processes In Organic Smentioning

confidence: 99%

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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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Section: Theoretical Description Of Electronic Processes In Organic Smentioning

confidence: 99%

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

Self Cite

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“…Besides, the side chains have capability to alter the characteristic energy profiles of polymers by enhancing or diminishing various vital characteristics like tuning of solubility, thermal stability of BHJ OSCs, impacting the rate of crystallization and dimerization of fullerene, electron affinity, polymer packing, morphology, eventually device efficiency and others [19,[23][24][25][26][27][28] . As compared to the electron-donating alkyl side chain, the electron-withdrawing ester linked side chain group is very impactful in lowering the HOMO energy level with increased crystallinity and exhibiting high density of π -π * stacking.…”

Section: Introductionmentioning

confidence: 99%

Low-bandgap polymers with quinoid unit as π bridge for high-performance solar cells

Shahid

Yuan

Wang

et al. 2020

Journal of Energy Chemistry

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“…17,18 Charge carrier mobility is highly influenced by the morphology of materials and intermolecular interaction of molecules in films. 19 There is need to synthesize PDI derivatives to generate photoluminescent (PL) charge transfer (CT) excitons. Therefore, to overcome these drawbacks, various groups are working through molecular designing, resulting in photoluminescent aggregates with facilitated charge transport and also developing new routes for the fabrication of air-stable organic devices.…”

Section: Introductionmentioning

confidence: 99%

Facile Synthesis and Evaluation of Electron Transport and Photophysical Properties of Photoluminescent PDI Derivatives

Naqvi

Kumar

2019

ACS Omega

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Perylenediimides (PDIs) have emerged as potential materials for optoelectronic applications. In the current work, four PDI derivatives, substituted at imide nitrogen with 2,6-diisopropyl phenyl, 2-nitrophenyl, diphenylmethylene, and pentafluorophenyl groups, have been synthesized from perylene 3,4,9,10-tetracarboxylic dianhydride using a facile imidization synthesis process. PDI derivatives have been spectroscopically characterized for their structure and optical properties. Temperature-variable absorption and emission spectroscopy study confirmed the H-aggregation property. H-aggregation along with strong emission suggests the slipped π–π stacking of PDI molecules. Electrochemical analysis was performed for their redox behavior and calculation of lowest unoccupied molecular orbital and highest occupied molecular orbital energy levels. Scanning electron microscopy showed the formation of ordered structures. The PDI derivatives showed excellent electron conductivity without doping and 5–10× higher electron mobility than that of state-of-the-art fullerene acceptor phenyl-C61-butyric acid methyl ester (PC61BM). Finally, the charge generation and charge transfer phenomenon was studied by transient absorption spectroscopy (TAS). TAS showed ultrafast charge transfer from the poly(3-hexyl)thiophene (P3HT) donor polymer to PDI and formation of long-lived charge-separated states similar to fullerene derivative PC61BM/P3HT blends. Such PDI derivatives with excellent solubility and photophysical and electronic properties are potential n-type materials to be used in organic electronic devices.

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Impact of alkyl chain branching positions on molecular packing and electron transport of dimeric perylenediimide derivatives

Cited by 21 publications

References 68 publications

Origin of Photocurrent and Voltage Losses in Organic Solar Cells

Origin of Photocurrent and Voltage Losses in Organic Solar Cells

Low-bandgap polymers with quinoid unit as π bridge for high-performance solar cells

Facile Synthesis and Evaluation of Electron Transport and Photophysical Properties of Photoluminescent PDI Derivatives

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