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Macroscopic and high-throughput printing of aligned nanostructured polymer semiconductors for MHz large-area electronics.

Bucella SG, Luzio A, Gann E, Thomsen L, McNeill CR, Pace G, Perinot A, Chen Z, Facchetti A, Caironi M - Nat Commun (2015)

Bottom Line: As opposed to the deposition of highly crystalline films, orientational alignment of polymer chains, albeit commonly achieved by non-scalable/slow bulk alignment schemes, is a more robust approach towards large-area electronics.Our approach enables directional self-assembling of polymer chains exhibiting large transport anisotropy and a mobility up to 6.4 cm(2) V(-1) s(-1), allowing very simple device architectures to operate at 3.3 MHz.Thus, the proposed deposition strategy is exceptionally promising for mass manufacturing of high-performance polymer circuits.

View Article: PubMed Central - PubMed

Affiliation: Center for Nano Science and Technology @PoliMi, Istituto Italiano di Tecnologia, Via Pascoli 70/3, Milano 20133, Italy.

ABSTRACT
High-mobility semiconducting polymers offer the opportunity to develop flexible and large-area electronics for several applications, including wearable, portable and distributed sensors, monitoring and actuating devices. An enabler of this technology is a scalable printing process achieving uniform electrical performances over large area. As opposed to the deposition of highly crystalline films, orientational alignment of polymer chains, albeit commonly achieved by non-scalable/slow bulk alignment schemes, is a more robust approach towards large-area electronics. By combining pre-aggregating solvents for formulating the semiconductor and by adopting a room temperature wired bar-coating technique, here we demonstrate the fast deposition of submonolayers and nanostructured films of a model electron-transporting polymer. Our approach enables directional self-assembling of polymer chains exhibiting large transport anisotropy and a mobility up to 6.4 cm(2) V(-1) s(-1), allowing very simple device architectures to operate at 3.3 MHz. Thus, the proposed deposition strategy is exceptionally promising for mass manufacturing of high-performance polymer circuits.

No MeSH data available.


Polarized optical density and charge modulation microscopy maps.13 × 24 μm2 polarized optical density (OD) map (a) and 18 × 18 μm2 CMM map (b) with the indication of the polymers backbone orientation (black dashed lines) and the relative degree of orientational order maps (c,d) of a bar-coated film. On the top of the picture the direction of printing with respect to the maps is reported. Scale bars, 4 μm. The mean DR values are calculated relative to these scanned areas.
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f5: Polarized optical density and charge modulation microscopy maps.13 × 24 μm2 polarized optical density (OD) map (a) and 18 × 18 μm2 CMM map (b) with the indication of the polymers backbone orientation (black dashed lines) and the relative degree of orientational order maps (c,d) of a bar-coated film. On the top of the picture the direction of printing with respect to the maps is reported. Scale bars, 4 μm. The mean DR values are calculated relative to these scanned areas.

Mentions: Interestingly, the large observed anisotropy for the bar-coated films is not accompanied by a significant optical dichroic ratio (DR), as measured by polarized ultraviolet–vis absorption spectroscopy (never superior to 1.8, Supplementary Fig. 14). This is in contrast to general thinking and it is far less intuitive to rationalize than in more highly optically aligned samples22. A possible way to solve this apparent discrepancy is to hypothesize a superior chain alignment of the film polymer surface with respect to the bulk, which would be consistent with the structural data and with a previous study confirming a different surface structure in P(NDI2OD-T2) films44. Thus, we utilized polarized charge modulation microscopy (p-CMM)5960, which maps the TDM of specific charge-induced transitions, and relates it to the preferential in-plane alignment of the polymer backbone. Being selective to charge-induced features, p-CMM is sensitive only to the conjugated segments that are involved in the charge transport. p-CMM maps can further be compared with polarized confocal microscopy (pCM) maps, providing instead information of the average alignment of all conjugated segments of the film. By adopting a polarized beam at 690 nm, close to the main optical absorption peak of P(NDI2OD-T2) in the visible (Supplementary Fig. 14), maps of the orientation (Fig. 5a,b) and of the Degree of orientational Order (DO; Fig. 5c,d) of the TDM from pCM (Fig. 5a,c) and p-CMM (Fig. 5b,d) are measured in the same channel area of a working FET. In P(NDI2OD-T2) the dipole moment of the electronic transition probed at 690 nm oscillates parallel to the polymer backbone60, therefore maps in Fig. 5a,b are directly informative of the polymer backbone orientation within the film. Figure 5a confirms that a clear preferential alignment of the polymer backbones along the printing direction occurs, with a mean DO of 56%. From the value, the mean optical DR can be extracted using the formula , resulting in a value of 3.5 for pCM. Already by comparing the maps in Fig. 5a,b it can be observed that the conjugated segments probed with p-CMM appear to be more finely aligned along the coating direction. Quite remarkably, for p-CMM a value of 98% can be extracted, corresponding to a very high of 99, univocally rationalizing the observed transport anisotropy. Such a high DR is only in part ascribable to a superior molecular alignment at the top semiconductor surface, since it is much larger than the value of 4.8 obtained by surface-sensitive NEXAFS. Therefore we can conclude that the high level of structural alignment is a prerogative of the P(NDI2OD-T2) chain fraction solely probed by charge accumulation, which effectively selects energetic sites within the most orientationally ordered phase of the channel. Thanks to p-CMM we have therefore unveiled the functional microstructure of bar-coated films, a very limited portion of conjugated segments at the interface with the dielectric which is responsible for the observed charge transport properties and tend to elude common structural investigations which are not selective to charged molecules.


Macroscopic and high-throughput printing of aligned nanostructured polymer semiconductors for MHz large-area electronics.

Bucella SG, Luzio A, Gann E, Thomsen L, McNeill CR, Pace G, Perinot A, Chen Z, Facchetti A, Caironi M - Nat Commun (2015)

Polarized optical density and charge modulation microscopy maps.13 × 24 μm2 polarized optical density (OD) map (a) and 18 × 18 μm2 CMM map (b) with the indication of the polymers backbone orientation (black dashed lines) and the relative degree of orientational order maps (c,d) of a bar-coated film. On the top of the picture the direction of printing with respect to the maps is reported. Scale bars, 4 μm. The mean DR values are calculated relative to these scanned areas.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4596007&req=5

f5: Polarized optical density and charge modulation microscopy maps.13 × 24 μm2 polarized optical density (OD) map (a) and 18 × 18 μm2 CMM map (b) with the indication of the polymers backbone orientation (black dashed lines) and the relative degree of orientational order maps (c,d) of a bar-coated film. On the top of the picture the direction of printing with respect to the maps is reported. Scale bars, 4 μm. The mean DR values are calculated relative to these scanned areas.
Mentions: Interestingly, the large observed anisotropy for the bar-coated films is not accompanied by a significant optical dichroic ratio (DR), as measured by polarized ultraviolet–vis absorption spectroscopy (never superior to 1.8, Supplementary Fig. 14). This is in contrast to general thinking and it is far less intuitive to rationalize than in more highly optically aligned samples22. A possible way to solve this apparent discrepancy is to hypothesize a superior chain alignment of the film polymer surface with respect to the bulk, which would be consistent with the structural data and with a previous study confirming a different surface structure in P(NDI2OD-T2) films44. Thus, we utilized polarized charge modulation microscopy (p-CMM)5960, which maps the TDM of specific charge-induced transitions, and relates it to the preferential in-plane alignment of the polymer backbone. Being selective to charge-induced features, p-CMM is sensitive only to the conjugated segments that are involved in the charge transport. p-CMM maps can further be compared with polarized confocal microscopy (pCM) maps, providing instead information of the average alignment of all conjugated segments of the film. By adopting a polarized beam at 690 nm, close to the main optical absorption peak of P(NDI2OD-T2) in the visible (Supplementary Fig. 14), maps of the orientation (Fig. 5a,b) and of the Degree of orientational Order (DO; Fig. 5c,d) of the TDM from pCM (Fig. 5a,c) and p-CMM (Fig. 5b,d) are measured in the same channel area of a working FET. In P(NDI2OD-T2) the dipole moment of the electronic transition probed at 690 nm oscillates parallel to the polymer backbone60, therefore maps in Fig. 5a,b are directly informative of the polymer backbone orientation within the film. Figure 5a confirms that a clear preferential alignment of the polymer backbones along the printing direction occurs, with a mean DO of 56%. From the value, the mean optical DR can be extracted using the formula , resulting in a value of 3.5 for pCM. Already by comparing the maps in Fig. 5a,b it can be observed that the conjugated segments probed with p-CMM appear to be more finely aligned along the coating direction. Quite remarkably, for p-CMM a value of 98% can be extracted, corresponding to a very high of 99, univocally rationalizing the observed transport anisotropy. Such a high DR is only in part ascribable to a superior molecular alignment at the top semiconductor surface, since it is much larger than the value of 4.8 obtained by surface-sensitive NEXAFS. Therefore we can conclude that the high level of structural alignment is a prerogative of the P(NDI2OD-T2) chain fraction solely probed by charge accumulation, which effectively selects energetic sites within the most orientationally ordered phase of the channel. Thanks to p-CMM we have therefore unveiled the functional microstructure of bar-coated films, a very limited portion of conjugated segments at the interface with the dielectric which is responsible for the observed charge transport properties and tend to elude common structural investigations which are not selective to charged molecules.

Bottom Line: As opposed to the deposition of highly crystalline films, orientational alignment of polymer chains, albeit commonly achieved by non-scalable/slow bulk alignment schemes, is a more robust approach towards large-area electronics.Our approach enables directional self-assembling of polymer chains exhibiting large transport anisotropy and a mobility up to 6.4 cm(2) V(-1) s(-1), allowing very simple device architectures to operate at 3.3 MHz.Thus, the proposed deposition strategy is exceptionally promising for mass manufacturing of high-performance polymer circuits.

View Article: PubMed Central - PubMed

Affiliation: Center for Nano Science and Technology @PoliMi, Istituto Italiano di Tecnologia, Via Pascoli 70/3, Milano 20133, Italy.

ABSTRACT
High-mobility semiconducting polymers offer the opportunity to develop flexible and large-area electronics for several applications, including wearable, portable and distributed sensors, monitoring and actuating devices. An enabler of this technology is a scalable printing process achieving uniform electrical performances over large area. As opposed to the deposition of highly crystalline films, orientational alignment of polymer chains, albeit commonly achieved by non-scalable/slow bulk alignment schemes, is a more robust approach towards large-area electronics. By combining pre-aggregating solvents for formulating the semiconductor and by adopting a room temperature wired bar-coating technique, here we demonstrate the fast deposition of submonolayers and nanostructured films of a model electron-transporting polymer. Our approach enables directional self-assembling of polymer chains exhibiting large transport anisotropy and a mobility up to 6.4 cm(2) V(-1) s(-1), allowing very simple device architectures to operate at 3.3 MHz. Thus, the proposed deposition strategy is exceptionally promising for mass manufacturing of high-performance polymer circuits.

No MeSH data available.