Tuning Organic Semiconductor Alignment and Aggregation via Nanoconfinement

Haruk, Alexander M.; Leng, Collen Z.; Fernando, Pravini S.; Smilgies, Detlef‐M.; Loo, Yueh‐Lin; Mativetsky, Jeffrey M.

doi:10.1021/acs.jpcc.0c06270

Cited by 7 publications

(16 citation statements)

References 85 publications

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“…Seeded nucleation from these aligned layers may extend such thin-film order to a third dimension, but not over a sufficiently large length scale. Indeed, ordered thin films of conjugated polymers have been fabricated through epitaxial synthesis [19] and crystal growth, [20,21] solidification using volatile additives, [21,22] crystallization on top of an alignment layer (i.e., mesoepitaxy) [23][24][25] or from the melt in planar [26,27] or vertical [28] nanoconfinement, as well as sequential assembly of crystalline domains by directional coating. [29,30] Post deposition treatments via, e.g., solvent vapor annealing, was also successful.…”

Section: Introductionmentioning

confidence: 99%

Conjugated Polymer Mesocrystals with Structural and Optoelectronic Coherence and Anisotropy in Three Dimensions

Pavlica

et al. 2021

Advanced Materials

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Semiconducting mesocrystalline bulk polymer specimens that exhibit near‐intrinsic properties using channel‐die pressing are demonstrated. A predominant edge‐on orientation is obtained for poly(3‐hexylthiophene‐2,5‐diyl) (P3HT) throughout 2 mm‐thick/wide samples. This persistent mesocrystalline arrangement at macroscopic scales allows reliable evaluation of the electronic charge‐transport anisotropy along all three crystallographic axes, with high mobilities found along the π‐stacking. Indeed, charge‐carrier mobilities of up to 2.3 cm2 V−1 s−1 are measured along the π‐stack, which are some of the highest mobilities reported for polymers at low charge‐carrier densities (drop‐cast films display mobilities of maximum ≈10−3 cm2 V−1 s−1). The structural coherence also leads to an unusually well‐defined photoluminescence line‐shape characteristic of an H‐aggregate (measured from the surface perpendicular to the materials flow), rather than the typical HJ‐aggregate feature usually found for P3HT. The approach is widely applicable: to electrical conductors and materials used in n‐type devices, such as poly{[N,N′‐bis(2‐octyldodecyl)‐naphthalene‐1,4,5,8‐bis(dicarboximide)‐2,6‐diyl]‐alt‐5,5′‐(2,2′‐bithiophene)} (N2200) where the mesocrystalline structure leads to high electron transport along the polymer backbones (≈1.3 cm2 V−1 s−1). This versatility and the broad applicability of channel‐die pressing signifies its promise as a straightforward, readily scalable method to fabricate bulk semiconducting polymer structures at macroscopic scales with properties typically accessible only by the tedious growth of single crystals.

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Section: Introductionmentioning

confidence: 99%

Conjugated Polymer Mesocrystals with Structural and Optoelectronic Coherence and Anisotropy in Three Dimensions

Pavlica

et al. 2021

Advanced Materials

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“…The (010) peak became more pronounced as the nanowire diameter was reduced (see Supporting Information Figure S6), which is consistent with the observed increase in the relative amount of (201) orientation as the pore size was reduced for the intemplate samples. 73 In the case of P3HT confined in 18 nm nanopores (Figure 2j), a (100) ring is visible, with an intensity that is most prominent along the q xy axis. An angularly broad (010) peak is also visible along the meridian.…”

mentioning

confidence: 96%

“…We have recently developed a versatile solution-based slow infiltration process with slow solvent evaporation 73 for preparing organic semiconducting nanowires within nanoporous anodic aluminum oxide (AAO) membranes bearing parallel monodisperse cylindrical nanopores. The process's slow solvent drying (>24 h) leads to the formation of solid, crystalline nanowires.…”

mentioning

confidence: 99%

“…As discussed in our recent study of in-template nanowires grown by solution infiltration with slow evaporation, two coexisting preferred crystallographic orientations are present in each of these systems. 73 For TIPS-Pn, the Form I polymorph is observed with [032̅ ] (π−π stacking) and [001] (alkyl stacking) aligned with the axis of the nanowires (see Figure 2c). In the case of p-DTS(FBTTh 2 ) 2 , [141] (π−π stacking) and [201] growth are favored along the nanowire axis (see Figure 2f).…”

mentioning

confidence: 99%

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Freeing Organic Semiconductor Nanowires from Nanoporous Aluminum Oxide Templates: Effects on Morphology, Crystal Structure, and Molecular Aggregation

Haruk

Fernando

Smilgies

et al. 2021

Crystal Growth & Design

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Nanoconfinement of organic semiconductors in nanoporous templates is promising for manipulating polymorphism and molecular orientation while forming nanowires with controlled dimensions. To harness the potential advantages of templated organic semiconductor nanowires, there is a need to understand the factors that influence final nanowire structure. Little is known, however, about the extent to which nanowire morphology and internal structure are impacted by nanowire release from the boundary conditions imposed by the template. To address this knowledge gap, we assessed the morphological, crystallographic, and photophysical changes that occur in three common organic semiconductors in response to nanoporous template removal [(Bis(triisopropylsilylethynyl)pentacene (TIPS-Pn), (7,7′-[4,4-Bis(2-ethylhexyl)-4H-silolo[3,2-b:4,5-b′]dithiophene-2,6-diyl]bis[6-fluoro-4-(5′-hexyl-[2,2′-bithiophen]-5-yl)benzo[c][1,2,5]thiadiazole] (p-DTS(FBTTh2)2), and poly(3-hexylthiophene) (P3HT)]. Although the nanowires comprising planar small molecules maintained their cylindrical shape following template removal, the investigated polymer, P3HT, exhibited extensive nanowire fusing for pore sizes of 55 nm and below, leading to a networked structure. All three systems presented preferred crystallite orientations that persisted in the freed nanowires. Nanowires generally exhibited an increasingly J-like aggregation character following template removal. Collectively, these results reveal that subtle molecular rearrangement takes place in the small molecule systems, while significant structural rearrangement can occur in polymer systems in response to template removal.

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“…usually soluble in organic solvent so that they can be solution processed by employing simple techniques like spin-coating and ink-jet printing. Moreover, the photophysical proprieties of organic semiconductors can be modified by chemical synthesis [15][16][17][18].…”

Section: Introductionmentioning

confidence: 99%

Excitation Dynamics and Losses in Solution Processed Disordered Semiconductors

Zarrabi¹

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From a technological point of view, organic semiconductor-based devices are of significant interest due to their light weight, ease of processability, conformal flexibility and potentially low cost and low embodied energy pro-duction. Motivated by these quite unique selling points, the performance of organic semiconductors has been a subject of multi-disciplinary study for more than 60 years with steady progress in applications such as solar cells, transistors, light emitting diodes and various sensors. One of the main characteristics that governs the performance of organic semiconduc-tors is their low dielectric constants, meaning they are excitonic at room temperature. A second main feature that dictates the charge carrier recom-bination and transport properties is the disordered nature of these semicon-ductors causing low charge carrier mobilities. The work described in this thesis focuses on these defining elements, and particularly their implications on photovoltaic devices. The discussion will start with a review into the main electro-optical phenomena in organic solar cells. Subsequently, a new method is presented for measuring exciton diffusion lengths based upon a low-quencher-content device structure. An anomalously large quenching volume is observed that can be assigned to long-range exciton delocaliza-tion prior to thermalization. These ultra-low-impurity content organic so-lar cells are also very useful as model systems to study and engineer trap states. Using this approach, it is found that mid-gap trap states are a universal feature in organic semiconductor donor-acceptor blends and un-expectedly contribute to charge generation and recombination. This has a profound impact on the thermodynamic limit of organic photovoltaic de-vices. Having demonstrated this important new insight it is further shown that a definitive link exists between a reduced recombination rate compared to the Langevin rate in some exceptional, high performance material sys-tems and a significant increase in the dissociation rate of charge transfer states upon post-processing of the active layer. In sum, the work presented in this thesis delivers important new insight as to the underlying dynamics of exciton generation and diffusion, charge transfer state dissociation, and indeed the ultimate fate of photogenerated free carriers.

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Tuning Organic Semiconductor Alignment and Aggregation via Nanoconfinement

Cited by 7 publications

References 85 publications

Conjugated Polymer Mesocrystals with Structural and Optoelectronic Coherence and Anisotropy in Three Dimensions

Conjugated Polymer Mesocrystals with Structural and Optoelectronic Coherence and Anisotropy in Three Dimensions

Freeing Organic Semiconductor Nanowires from Nanoporous Aluminum Oxide Templates: Effects on Morphology, Crystal Structure, and Molecular Aggregation

Excitation Dynamics and Losses in Solution Processed Disordered Semiconductors

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