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Flow-enhanced solution printing of all-polymer solar cells.

Diao Y, Zhou Y, Kurosawa T, Shaw L, Wang C, Park S, Guo Y, Reinspach JA, Gu K, Gu X, Tee BC, Pang C, Yan H, Zhao D, Toney MF, Mannsfeld SC, Bao Z - Nat Commun (2015)

Bottom Line: Our flow design resulted in a ∼90% increase in the donor thin film crystallinity and reduced microphase separated donor and acceptor domain sizes.The improved morphology enhanced all metrics of solar cell device performance across various printing conditions, specifically leading to higher short-circuit current, fill factor, open circuit voltage and significantly reduced device-to-device variation.We expect our design concept to have broad applications beyond all-polymer solar cells because of its simplicity and versatility.

View Article: PubMed Central - PubMed

Affiliation: 1] Department of Chemical Engineering, Stanford University, Stanford, California 94305, USA [2] Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA.

ABSTRACT
Morphology control of solution coated solar cell materials presents a key challenge limiting their device performance and commercial viability. Here we present a new concept for controlling phase separation during solution printing using an all-polymer bulk heterojunction solar cell as a model system. The key aspect of our method lies in the design of fluid flow using a microstructured printing blade, on the basis of the hypothesis of flow-induced polymer crystallization. Our flow design resulted in a ∼90% increase in the donor thin film crystallinity and reduced microphase separated donor and acceptor domain sizes. The improved morphology enhanced all metrics of solar cell device performance across various printing conditions, specifically leading to higher short-circuit current, fill factor, open circuit voltage and significantly reduced device-to-device variation. We expect our design concept to have broad applications beyond all-polymer solar cells because of its simplicity and versatility.

No MeSH data available.


Related in: MedlinePlus

Polymer crystallinity analysis via GIXD.(a) Comparison of the diffraction patterns between the FLUENCE-printed and the reference films for neat donor polymer films and the blend films. The π–π stacking peak and the lamella peaks are labelled as (010) and (100) to (200), respectively. (Inset) Magnified images of the (100) peak (geometrical correction not applied here so as to clearly show the intensity difference). Across all images, the intensity is scaled by exposure time and the irradiated volume, to allow visual comparison of the peak intensities. Films were printed at 25 μm s−1 from 7 mg ml−1 chlorobenzene solution at 50 °C. The average film thickness was 124 nm. GIXD was taken with the printing direction of the films oriented parallel to the incident beam (shown here) as well as perpendicular to the incident beam (Supplementary Fig. 3). (b) Comparison of geometrically corrected orientation distribution functions at various printing speeds (25–100 μm s−1) in neat donor polymer films. The geometrical correction was performed on pole figures shown in Supplementary Fig. 2. The corrected intensity of the (010) peak, or sin(χ)I(χ), represents the relative population of the crystallites with a particular orientation χ, the polar angle (Supplementary Fig. 1). In this plot, χ=0° indicates face-on orientation and χ=90° indicates edge-on orientation. The relative orientation of the crystallite at corresponding χ is shown as inset. The red and blue curves correspond to films printed with and without FLUENCE, respectively. The relative degree of crystallinity is obtained by integrating the area below each curve. From left to right, the rdoc is 89%, 94%, 87%, respectively. The error bars were from the s.d.s from the fitted (010) peak areas (Supplementary Fig. 1). For most data points, the error bars are too small to be visible.
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f2: Polymer crystallinity analysis via GIXD.(a) Comparison of the diffraction patterns between the FLUENCE-printed and the reference films for neat donor polymer films and the blend films. The π–π stacking peak and the lamella peaks are labelled as (010) and (100) to (200), respectively. (Inset) Magnified images of the (100) peak (geometrical correction not applied here so as to clearly show the intensity difference). Across all images, the intensity is scaled by exposure time and the irradiated volume, to allow visual comparison of the peak intensities. Films were printed at 25 μm s−1 from 7 mg ml−1 chlorobenzene solution at 50 °C. The average film thickness was 124 nm. GIXD was taken with the printing direction of the films oriented parallel to the incident beam (shown here) as well as perpendicular to the incident beam (Supplementary Fig. 3). (b) Comparison of geometrically corrected orientation distribution functions at various printing speeds (25–100 μm s−1) in neat donor polymer films. The geometrical correction was performed on pole figures shown in Supplementary Fig. 2. The corrected intensity of the (010) peak, or sin(χ)I(χ), represents the relative population of the crystallites with a particular orientation χ, the polar angle (Supplementary Fig. 1). In this plot, χ=0° indicates face-on orientation and χ=90° indicates edge-on orientation. The relative orientation of the crystallite at corresponding χ is shown as inset. The red and blue curves correspond to films printed with and without FLUENCE, respectively. The relative degree of crystallinity is obtained by integrating the area below each curve. From left to right, the rdoc is 89%, 94%, 87%, respectively. The error bars were from the s.d.s from the fitted (010) peak areas (Supplementary Fig. 1). For most data points, the error bars are too small to be visible.

Mentions: First, we characterize how FLUENCE alters polymer crystallinity in printed thin films using grazing incidence X-ray diffraction (GIXD). The crystallinity of the blend films is relevant for the donor polymer PII-tT-PS5, since the acceptor polymer P(TP) remains amorphous at all tested conditions15 and only contributes to the amorphous halo in the GIXD patterns (Fig. 2). Most strikingly, both the π–π stacking peak (010) and the lamella stacking peak (100) of the donor polymer exhibit substantially higher intensities in FLUENCE-printed films, for both neat donor polymer films and the blend films. This qualitative observation indicates that our flow design has effectively enhanced the degree of crystallinity in the printed thin films as hypothesized (Fig. 2a). We further quantified the increase in the relative degree of crystallinity (rdoc) as discussed below. The observed increase in rdoc is corroborated with the changes in molecular packing distances due to FLUENCE (Supplementary Table 1). The lamella stacking distance is shorter in the FLUENCE-printed thin film by 2–3% as compared with that of the reference film at the same printing speed, and this trend persists across the printing speeds. In addition, the lamella stacking distance decreases with an increase of printing speed in neat polymer donor films. These observations imply that the side chains become increasingly close-packed with the increase of shear rate and/or the introduction of extensional flow. The closer packing may result from either a higher degree of ordering or a higher extent of side chain interdigitation.


Flow-enhanced solution printing of all-polymer solar cells.

Diao Y, Zhou Y, Kurosawa T, Shaw L, Wang C, Park S, Guo Y, Reinspach JA, Gu K, Gu X, Tee BC, Pang C, Yan H, Zhao D, Toney MF, Mannsfeld SC, Bao Z - Nat Commun (2015)

Polymer crystallinity analysis via GIXD.(a) Comparison of the diffraction patterns between the FLUENCE-printed and the reference films for neat donor polymer films and the blend films. The π–π stacking peak and the lamella peaks are labelled as (010) and (100) to (200), respectively. (Inset) Magnified images of the (100) peak (geometrical correction not applied here so as to clearly show the intensity difference). Across all images, the intensity is scaled by exposure time and the irradiated volume, to allow visual comparison of the peak intensities. Films were printed at 25 μm s−1 from 7 mg ml−1 chlorobenzene solution at 50 °C. The average film thickness was 124 nm. GIXD was taken with the printing direction of the films oriented parallel to the incident beam (shown here) as well as perpendicular to the incident beam (Supplementary Fig. 3). (b) Comparison of geometrically corrected orientation distribution functions at various printing speeds (25–100 μm s−1) in neat donor polymer films. The geometrical correction was performed on pole figures shown in Supplementary Fig. 2. The corrected intensity of the (010) peak, or sin(χ)I(χ), represents the relative population of the crystallites with a particular orientation χ, the polar angle (Supplementary Fig. 1). In this plot, χ=0° indicates face-on orientation and χ=90° indicates edge-on orientation. The relative orientation of the crystallite at corresponding χ is shown as inset. The red and blue curves correspond to films printed with and without FLUENCE, respectively. The relative degree of crystallinity is obtained by integrating the area below each curve. From left to right, the rdoc is 89%, 94%, 87%, respectively. The error bars were from the s.d.s from the fitted (010) peak areas (Supplementary Fig. 1). For most data points, the error bars are too small to be visible.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4557117&req=5

f2: Polymer crystallinity analysis via GIXD.(a) Comparison of the diffraction patterns between the FLUENCE-printed and the reference films for neat donor polymer films and the blend films. The π–π stacking peak and the lamella peaks are labelled as (010) and (100) to (200), respectively. (Inset) Magnified images of the (100) peak (geometrical correction not applied here so as to clearly show the intensity difference). Across all images, the intensity is scaled by exposure time and the irradiated volume, to allow visual comparison of the peak intensities. Films were printed at 25 μm s−1 from 7 mg ml−1 chlorobenzene solution at 50 °C. The average film thickness was 124 nm. GIXD was taken with the printing direction of the films oriented parallel to the incident beam (shown here) as well as perpendicular to the incident beam (Supplementary Fig. 3). (b) Comparison of geometrically corrected orientation distribution functions at various printing speeds (25–100 μm s−1) in neat donor polymer films. The geometrical correction was performed on pole figures shown in Supplementary Fig. 2. The corrected intensity of the (010) peak, or sin(χ)I(χ), represents the relative population of the crystallites with a particular orientation χ, the polar angle (Supplementary Fig. 1). In this plot, χ=0° indicates face-on orientation and χ=90° indicates edge-on orientation. The relative orientation of the crystallite at corresponding χ is shown as inset. The red and blue curves correspond to films printed with and without FLUENCE, respectively. The relative degree of crystallinity is obtained by integrating the area below each curve. From left to right, the rdoc is 89%, 94%, 87%, respectively. The error bars were from the s.d.s from the fitted (010) peak areas (Supplementary Fig. 1). For most data points, the error bars are too small to be visible.
Mentions: First, we characterize how FLUENCE alters polymer crystallinity in printed thin films using grazing incidence X-ray diffraction (GIXD). The crystallinity of the blend films is relevant for the donor polymer PII-tT-PS5, since the acceptor polymer P(TP) remains amorphous at all tested conditions15 and only contributes to the amorphous halo in the GIXD patterns (Fig. 2). Most strikingly, both the π–π stacking peak (010) and the lamella stacking peak (100) of the donor polymer exhibit substantially higher intensities in FLUENCE-printed films, for both neat donor polymer films and the blend films. This qualitative observation indicates that our flow design has effectively enhanced the degree of crystallinity in the printed thin films as hypothesized (Fig. 2a). We further quantified the increase in the relative degree of crystallinity (rdoc) as discussed below. The observed increase in rdoc is corroborated with the changes in molecular packing distances due to FLUENCE (Supplementary Table 1). The lamella stacking distance is shorter in the FLUENCE-printed thin film by 2–3% as compared with that of the reference film at the same printing speed, and this trend persists across the printing speeds. In addition, the lamella stacking distance decreases with an increase of printing speed in neat polymer donor films. These observations imply that the side chains become increasingly close-packed with the increase of shear rate and/or the introduction of extensional flow. The closer packing may result from either a higher degree of ordering or a higher extent of side chain interdigitation.

Bottom Line: Our flow design resulted in a ∼90% increase in the donor thin film crystallinity and reduced microphase separated donor and acceptor domain sizes.The improved morphology enhanced all metrics of solar cell device performance across various printing conditions, specifically leading to higher short-circuit current, fill factor, open circuit voltage and significantly reduced device-to-device variation.We expect our design concept to have broad applications beyond all-polymer solar cells because of its simplicity and versatility.

View Article: PubMed Central - PubMed

Affiliation: 1] Department of Chemical Engineering, Stanford University, Stanford, California 94305, USA [2] Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA.

ABSTRACT
Morphology control of solution coated solar cell materials presents a key challenge limiting their device performance and commercial viability. Here we present a new concept for controlling phase separation during solution printing using an all-polymer bulk heterojunction solar cell as a model system. The key aspect of our method lies in the design of fluid flow using a microstructured printing blade, on the basis of the hypothesis of flow-induced polymer crystallization. Our flow design resulted in a ∼90% increase in the donor thin film crystallinity and reduced microphase separated donor and acceptor domain sizes. The improved morphology enhanced all metrics of solar cell device performance across various printing conditions, specifically leading to higher short-circuit current, fill factor, open circuit voltage and significantly reduced device-to-device variation. We expect our design concept to have broad applications beyond all-polymer solar cells because of its simplicity and versatility.

No MeSH data available.


Related in: MedlinePlus