P3HT-b-PEO Hybrid Films

Subscriber access provided by MIDWESTERN UNIVERSITY

Surfaces, Interfaces, and Applications

Morphology Tuning of ZnO/P3HT/P3HT-b-PEO Hybrid Films Deposited via Spray or Spin Coating Kun Wang, Nuri Hohn, Lucas Kreuzer, Tobias Widmann, Martin Haese, Jean-Francois Moulin, and Peter Muller-Buschbaum ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.9b00599 • Publication Date (Web): 22 Feb 2019 Downloaded from http://pubs.acs.org on February 23, 2019

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 27 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Applied Materials & Interfaces

Morphology Tuning of ZnO/P3HT/P3HT-b-PEO Hybrid Films Deposited via Spray or Spin Coating Kun Wanga, Nuri Hohna, Lucas P. Kreuzera, Tobias Widmanna, Martin Haeseb, Jean-Francois Moulinb, Peter Müller-Buschbauma,c,*

aLehrstuhl

für Funktionelle Materialien, Physik-Department, Technische Universität München,

James-Franck-Str. 1, 85748 Garching, Germany bHelmholtz-Zentrum

Geesthacht at Heinz Maier-Leibnitz Zentrum, Lichtenbergstr. 1, 85747

Garching, Germany cHeinz

Maier-Leibnitz Zentrum (MLZ), Technische Universität München, Lichtenbergstr. 1,

85748 Garching, Germany

KEYWORDS: ZnO/P3HT/P3HT-b-PEO, morphology, spray coating, spin coating, TOF-GISANS

ABSTRACT Hybrid films of zinc oxide (ZnO) and poly(3-hexylthiophen-2,5-diyl) (P3HT) show promising characteristics for application in hybrid bulk heterojunction solar cells (HBSCs). However, the incompatibility of ZnO and P3HT may lead to a reduced interface area, thus reducing the probability of exciton separation and consequently lowering solar cells efficiencies. Here, a diblock copolymer P3HT-b-poly(ethylene oxide) (PEO) is introduced to improve the interface between ZnO and P3HT. ZnO is synthesized via a block copolymer assisted sol-gel approach and the used zinc precursor is directly incorporated into the PEO blocks. Thus, the possibility of

ACS Paragon Plus Environment

1

ACS Applied Materials & Interfaces 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 2 of 27

aggregation is reduced for both, the inorganic and the organic components and a good intermixing is ascertained. Two deposition methods, namely spray and spin coating are compared with respect to the resulting film structure, which is investigated with scanning electron microscopy (SEM) and time-of-flight grazing-incidence small-angle neutron scattering (TOF-GISANS) measurements. Both, the surface and inner morphologies reveal that the spin coated samples possess smaller and less diverse domain sizes than the sprayed films. Due to the advantage of spray coating in largescale production, the morphology of the sprayed samples is tailored more meticulous by changing the weight fraction of ZnO in the films. The sprayed hybrid films show smaller domains and less aggregation with decreasing amount of ZnO. This reveals that both, the deposition method and composition of the ZnO/P3HT/P3HT-b-PEO hybrid films play an important role for the film morphology and thus for improving the performance of HBSCs in future application.

1. INTRODUCTION Hybrid materials, such as polymer matrixes doped with multiple kinds of functional nanomaterials have gained great attention due to their promising thermal, mechanical, electric, optical and magnetic properties.1-4 Hence, these hybrid materials offer several application possibilities, such as optoelectronics,5,

6

photocatalysis,7 biomedical sensors,8,

9

energy storage10 and energy

conversion.11 Apart from these, one main branch of application is hybrid bulk-heterojunction solar cells (HBSCs), which offer outstanding potential due to the minor investment as compared to inorganic solar cells and the higher stability as compared to organic solar cells.12, 13 Based on extensive studies, HBSCs have demonstrated a great improvement in achieved power conversion efficiencies by taking advantage of the large surface-area-to-volume ratio of the embedded nanoparticles.13-15


2

Page 3 of 27 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


HBSCs, composed of a blend of conjugated polymers and inorganic semiconducting nanomaterials, are able to provide large interface areas and an increased probability for exciton dissociation at the hybrid interfaces within the exciton lifetime as compared to the conventional bilayer heterojunction layout. The generated excitons can only separate into charge carriers at the interfaces of polymer donor and inorganic acceptor, and the diffusion length for excitons in the polymer donor materials is limited within tens of nanometers.16, 17 Thus, the power conversion efficiency largely depends on the morphology of the donor and acceptor materials, which can be tailored by the material synthesis and the employed deposition methods. In inorganic and organic hybrid films, the two components tend to undergo an uncontrolled macrophase separation due to an energetically unfavorable interaction of the polymer with the inorganic semiconducting nanoparticles, which reduces the opportunity for exciton separation in HBSCs. Diblock copolymers with different functionalized blocks are deemed to be a promising additive to modify the morphology of the films by modifying the interfaces of organic and inorganic materials.18-21 With the introduction of a diblock copolymer, instead of an uncontrolled macrophase separation in a blend, microphase separation will occur due to the covalently bound two blocks of the block copolymer. Li et al. and Shi et al. improved the morphology of zinc oxide (ZnO)/poly(3-hexylthiophene) (P3HT) hybrid films by introducing the diblock copolymer poly(3hexylthiophene)-block-poly(ethylene oxide) (P3HT-b-PEO), achieving an improved photovoltaic performance.18, 19 They mixed ZnO, P3HT and P3HT-b-PEO in chlorobenzene, of which ZnO was prepared by the sol-gel method and dispersed in chlorobenzene beforehand. Thus, they needed two steps to fabricate hybrid films, since the solvents for dissolving ZnO and polymers are typically different due to the different polarities of the materials. In the present work, a significantly simpler synthesis method, namely a one pot synthesis, is developed as compared to these approaches from


3


Page 4 of 27

the literature,18, 19 for which, we mix directly the zinc precursor with P3HT and P3HT-b-PEO in a solvent mixture of dichlorobenzene (DCB) and dimethyl sulfoxide (DMSO). During the sol-gel process, ZnO nanoparticles from the zinc precursor directly grow in the PEO blocks, which avoids the aggregation of the ZnO nanoparticles as compared to the previously reported two-step method. The self-assembly of P3HT-b-PEO allows for a well-defined spacing of the obtained structures on a nanometer length scale. This morphology control is beneficial for increasing the interface area, and therefore increases the probability of exciton separation. Regarding the deposition methods, blade-coating, printing, spray deposition and spin coating are commonly used to fabricate sol-gel synthesized films. Spin coating is a technique with various advantages, such as easy operation, high deposition uniformity and fast processing time.22 Spray coating is also a widely used technique due to the possibility for large-scale production and a reduced material consumption as compared to spin coating.22, 23 Moreover, spray coating can be used to deposit films on non-flat surfaces. With each of these methods, continuous films with a well-defined structure on a nanometer length scale can be accessible. However, the interactions of the liquid flow with the substrate and the air, the evaporation rate and the nature of the blend system can lead to different morphologies for the different deposition methods. Although extensive work focused on morphological tuning of active layers in HBSCs, especially of the acceptor materials, few studies exist, which make a direct comparison of the film morphologies obtained by varying the deposition method. The blend of ZnO/P3HT/P3HT-b-PEO is fabricated in a sol-gel system, in which the diblock copolymer P3HT-b-PEO combines two functional units. The P3HT block acts as a charge carrier transport material in conjunction with the P3HT homopolymer, while the PEO block performs its role as a template for growing the ZnO nanoparticles from the precursor. In our previous work, we


4

Page 5 of 27 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


demonstrated that this diblock copolymer improves the interfaces of ZnO and P3HT greatly as compared to the morphology of the hybrid films without templating.24 In the present work, different deposition methods, namely spray and spin coating, are compared with respect to the obtained hybrid film morphologies. Given the industry relevance of spray coating, different weight ratios of ZnO are investigated for the sprayed samples to further improve the morphology of sprayed hybrid films. Since the exciton dissociation mostly occurs at the interface buried in the hybrid films and the inner morphology might be different from the surface morphology, a comprehensive investigation of the detailed structures of the hybrid films is crucial. Grazingincidence small-angle neutron scattering (GISANS) is a powerful tool to statistically investigate inner film structures.25,

26

In the time-of-flight (TOF) mode, a broad spectrum of neutron

wavelengths is used instead of a monochromatic neutron beam. After subsequent slicing the scattering spectrum in wavelength channels, a whole set of scattering patterns can be obtained with each pattern covering a different range of scattering vectors. Therefore, it is possible to detect multiple structures over a wide length scale range in one single time-of-flight grazing-incidence small-angle neutron scattering (TOF-GISANS) measurement. Moreover, taking advantage of variable wavelengths, both surface and inner morphologies are accessible by using TOFGISANS.27, 28 In order to visualize the morphology in real space, scanning electron microscopy (SEM) and optical microscopy (OM) are deployed. We demonstrate that with spray coating similar small nanostructures can be realized as in the common spin coating approach, which is beneficial for scaling up the hybrid film fabrication as needed in HBSC applications.

2. EXPERIMENTAL SECTION


5


Page 6 of 27

2.1 Materials. The diblock copolymer, poly(3-hexylthiophene)-block-poly(ethylene oxide) (P3HT-b-PEO) (Mn: 3-b-90 kg mol-1) with a polydispersity index (PDI) of 1.3, was purchased from Polymer Source Inc., Canada. Zinc acetate (99.99% trace metals basis), 1,2-dichlorobenzene (DCB, anhydrous, 99%), dimethyl sulfoxide (DMSO, anhydrous, ≥99.9%) and ethanolamine (MEA, 98%) were purchased from Sigma-Aldrich. All materials were used as received. 2.2 Sample Preparation. 20 mg of P3HT and 4 mg of P3HT-b-PEO were dissolved in a 2 mL solution, which was a mixture of DCB and DMSO (with a volume ratio of 7:1). The solution was stirred for 30 min to dissolve both polymers. At the same time, an appropriate amount of zinc acetate was dissolved in a separate vial in the same solvent mixture and stirred for 30 min. Afterwards, 24µL of MEA was added to the polymer solution and stirred further for 30 min. After mixing the zinc acetate solution with the polymer solution, further stirring for 1 h was carried out. All the stirring procedures were performed at 80 °C. Spray and spin coating were used to deposit the hybrid solution onto silicon (100) substrates, which were pre-cleaned in an acid bath for 15 min. For spray coating, an airbrush gun (Harder & Steenbeck GmbH & Co. KG, Grafo T3) was used. To avoid any blockage of the spray gun, the initial solution was diluted two times with the DCB/DMSO solvent mixture. The parameters used for the spray coating setup are given in the Supporting Information. Spin coating was carried out under ambient conditions at 1500 rpm for 60 sec. Finally, the hybrid films were annealed at 80 °C for 30 min to obtain well-organized hybrid films. The schematic representation of the hybrid film fabrication steps is shown in Figure 1.


6

Page 7 of 27 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 1. Schematic representation of the steps involved in the fabrication of the ZnO/P3HT/P3HT-b-PEO hybrid films via spray or spin coating and subsequent thermal annealing at 80 °C.

2.3 Film Characterization. Optical Microscopy (OM) was performed with an Axiolab A microscope (Carl Zeiss) equipped with a PixeLink USB Capture BE 2.6 chare coupled device (CCD) camera. Scanning electron microscopy (SEM) was carried out on a Zeiss Gemini Ultra Plus field emission SEM at an electron acceleration voltage of 3 kV. The film thickness was detected by a Bruker DektakXT stylus profiler. Grazing-incidence small-angle neutron scattering in the time-of-flight mode (TOF-GISANS) was performed at the REFSANS instrument at the Forschungs-Neutronenquelle Heinz Maier-Leibnitz (FRM II) in Garching, Germany.29, 30 Instead of a monochromatic neutron beam, a neutron beam with a wide range of wavelengths from 0.2 to 1.9 nm was used. A high-speed double chopper system was employed to define the neutron


7


Page 8 of 27

pulses.30 The neutron data were sliced into 22 wavelength channels with a wavelength resolution of 10 % for each channel.31 The scattering signal was recorded on a two-dimensional (2D) 3He detector with a sample-detector distance of 10.5 m.29 A beamstop was installed at the direct peak position in front of the detector to avoid saturation. The incident angle of the incoming neutron beam was kept at a constant value of 0.38°. The counting time for each sample was 20 h.

3. RESULTS AND DISCUSSION 3.1 Morphology Tuning by Deposition Method. OM images of ZnO/P3HT/P3HT-b-PEO hybrid films with the ratio of wZnO: wP3HT: wP3HT-b-PEO = 4:5:1 deposited by spray and spin coating are shown in Figure 2a-b. Despite having a constant ratio of the three components, the surface morphologies show obvious differences. The spray coated films show a large amount of ripples at the surface. Ripples induced by spray coating are mainly due to the complicated flow behavior in the liquid layer, which is widely reported in the literature.32-36 In the present study, the situation is complicated due to the used multicomponent solution. Having the substrate at elevated temperature causes a fast evaporation of residual solvent during spray deposition and thereby limits the probability of equilibrating height difference via a vertical flow on the substrate. Thus, spray coating creates less homogeneous films on a micrometer length scale as compared with spin coating. During the spin coating process, excess solution can be removed by the centrifugal forces.35 No ripples are observed for the hybrid films prepared via spin coating, instead, some black spots are randomly distributed at the surface, which can be attributed to the aggregations of small ZnO nanoparticles. To investigate the surface morphology on a nanometer length scale, SEM images of sprayed and spin coated samples are shown in Figure 2c and 2d, respectively. Due to the different contrast between ZnO and the polymers, ZnO particles


8

Page 9 of 27 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


appear bright, while polymers dark. Both, the films deposited by spray and spin coating exhibit a well-mixed structure on the nanoscale, which is expected to provide a large interface area for the exciton separation, while retaining interconnected pathways for charge carrier transport for application in HBSCs. Compared to the spray coated samples, the surface of spin coated films exhibits much smaller domains for both, ZnO clusters and polymer domains. Thus, OM and SEM images depict a more homogeneous morphology of ZnO/P3HT/P3HT-b-PEO hybrid films deposited via spin coating than the counterparts via spray coating on both, micrometer and nanometer length scale. Although, spray coating leads to a rougher surface structure, it is more important for large-scale production and deposition on non-flat surfaces. Hence, the morphology of sprayed films is further optimized.

Figure 2. OM (a, b) and SEM (c, d) images of ZnO/P3HT/P3HT-b-PEO hybrid films deposited by (a, c) spray coating and (b, d) spin coating.

The inner morphology of the hybrid films might be different from what we observe at the surface.37-39 Moreover, for HBSCs, the morphology inside the films is of great importance as excitons can only separate into negative and positive charge carriers at the interfaces of P3HT


9


Page 10 of 27

(light absorber and electron donor) and ZnO (electron acceptor). Thus, TOF-GISANS is used to probe the structure at both, the surface and inside the hybrid films.40 Additionally, TOF-GISANS has a high statistical relevance due to a large illumination area on the samples induced by the large size of the neutron beam in combination with the used small incident angle. Selected 2D GISANS data of the films deposited by spray and spin coating probed at different wavelengths are shown in Figure 3. The sample horizon shows the minimum intensity position, which is marked by a dashed line. Below the sample horizon, the scattering pattern originates from transmitted intensities, with the direct beam being shielded with a beamstop to prevent the detector from oversaturating. Above the sample horizon, the scattering pattern contains the GISANS signal.41 The specular peak is found in the GISANS part at the positon of the exit angle (αf) equal to the incident angle (αi). A slight shift towards smaller scattering angles of the specular beam is observed at longer neutron wavelengths due to the effect of gravity on the neutron beam, which is corrected in the data analysis.31, 42 Between the sample horizon and the specular peak, the Yoneda peak is detected which is located at the position of the critical angle αc. At short neutron wavelengths, the Yoneda peak is positioned far below the specular peak. Therefore, the whole volume of the thin films can be explored. When increasing the neutron wavelength, the position of Yoneda peak moves to higher scattering angles due to the increasing value of αc.43 For neutrons with long wavelengths, the Yoneda peak gradually overlaps with the specular peak. In such configuration, only surface structures at a scattering depth down to tens of nanometers can be probed. Thus, both the surface and inner morphologies are measured simultaneously with the TOF-GISANS experiment.


10

Page 11 of 27 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 3. Selected 2D GISANS data of the ZnO/P3HT/P3HT-b-PEO hybrid films deposited by (a-f) spray coating and (g-l) spin coating obtained from the TOF-GISANS measurements. The average neutron wavelength from left to right is (a, g) 0.38 nm, (b, h) 0.46 nm, (c, i) 0.57 nm, (d, j) 0.69 nm, (e, k) 0.85 nm, and (f, l) 1.03 nm, respectively. The direct beam is covered by a beamstop. The dashed black line in (a) illustrates the sample horizon. S, Y and DB in (a) represent specular peak, Yoneda peak and direct beam, respectively. The red arrows along the vertical and horizontal directions indicate the places where the vertical and horizontal line cuts are performed.

Vertical line cuts are performed at qy=0 nm-1 (marked by a red vertical arrow in Figure 3a), which contain the information about the film structure perpendicular to the substrate surface. The vertical line cuts for both spray and spin coated samples are shown in Figure 4. The neutron wavelength increases from bottom to top. For all curves, a drop in intensity at αi + αf = 0.38° is observed, which indicates the sample horizon. For angles αi + αf < 0.38°, the signal originates from the transmitted intensity. For angles αi + αf > 0.38°, the scattering signal originates from the reflected beam, with the specular peak located at αi + αf = 0.76°, twice the value of the incident angle, for all curves.


11


Page 12 of 27

Compared to spray coated films, the spin coated films show more intense specular peaks for all curves at different wavelengths, due to a smaller surface roughness and better homogeneity of the films produced by spin coating than those by spray coating. Another intense peak, the Yoneda peak, is located between the sample horizon and the specular peak (at small neutron wavelengths), which shifts to larger scattering angles with increasing neutron wavelength as marked by the dashed red line. For the spray coated samples, the rate of this shift is slightly larger than for the spin coated samples, indicating that with different deposition methods, different hybrid films form.

Figure 4. Vertical line cuts of the 2D GISANS data for the ZnO/P3HT/P3HT-b-PEO hybrid films deposited by (a) spray coating and (b) spin coating obtained from the 2D GISANS scattering pattern. From bottom to top, the average neutron wavelength increases from 0.38 to 1.14 nm. All curves are shifted along the y axis for clarity. The region shielded by the beamstop is illustrated in gray. The sample horizon (dashed black line), the shift of the Yoneda peak (dashed red line) and the specular peak (solid dark yellow line) are indicated, respectively.


12

Page 13 of 27 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 5 shows the linear relationship of the detected critical angles (Yoneda peak positions) and the neutron wavelengths for the hybrid films prepared via spray and spin coating as well as for reference bulk ZnO, P3HT and PEO, which are involved in the ZnO/P3HT/P3HT-b-PEO hybrid films. For the spray and spin coated hybrid films, the data are fitted according to the following equation αc = λ

𝜌 𝜋

(1)

with ρ being the neutron scattering length density (SLD) of the material.43 The critical angle position is only obtained from the vertical line cuts at short neutron wavelengths since the Yoneda peak overlaps with the high-intensity specular peak at long neutron wavelengths. The detected Yoneda peak position of both the spray and spin coated samples are larger than those of bulk P3HT and PEO, but smaller than bulk ZnO, indicating the successful mixture of ZnO, P3HT and PEO in the hybrid films. Moreover, the linear slope of the critical angle versus wavelength is slightly smaller for the spin coated sample (~0.43 deg. nm-1) as compared to the spray coated sample (~0.47 deg. nm-1), which implies a smaller SLD of the spin coated samples (~1.77x10-4 nm-2) as compared to the sprayed sample (~2.11x10-4 nm-2) according to equation (1). Thus, different deposition methods also cause different hybrid films to form. Moreover, both values are larger than the theoretical value (~1.13x10-4 nm-2) calculated from the theoretical SLD values and volume fractions of the three components. A possible explanation is a larger volume fraction of ZnO in the hybrid films as compared to the simple assumption from the used volume fraction of the initial materials.


13


Page 14 of 27

Figure 5. Experimental Yoneda peak positions (solid squares) of the hybrid films deposited by spray (dark yellow) and spin coating (purple) obtained from the vertical line cuts and corresponding linear fits to the data (solid lines). For comparison, the theoretical critical angle positions of bulk ZnO (black), P3HT (red) and PEO (blue) are included.

Lateral structures being present inside the hybrid films can be accessed due to the different scattering contrasts of the materials in the hybrid films.25, 42 Horizontal line cuts (marked by a red horizontal arrow in Figure 3a) are done at the Yoneda region for the films deposited via spray and spin coating. The cuts are depicted in Figure 6 with increasing neutron wavelength from bottom to top. Due to different neutron wavelengths, each horizontal line cut covers a different qy range, which makes it possible to probe a wide range of length scales. All horizontal line cuts are fitted with a model based on the Distorted-Wave Born Approximation (DWBA) in the framework of the effective interface approximation.44 We assume cylindrical-shaped scattering objects, in local monodisperse approximation (LMA), distributed on a one-dimensional paracrystal lattice to determine the most prominent length scales of the spatial distances and diameters of the detected domains.44 From the fits, form factors and structure factors are extracted, which are associated


14

Page 15 of 27 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


with the radius of the scattering objects and their corresponding center-to-center distances, respectively. For the sprayed samples, three prominent structures are required to fit the horizontal line cuts at different neutron wavelengths, namely large-sized, middle-sized and small-sized structures. For the spin coated samples, two structures (large-sized and small-sized structures) are sufficient to properly fit all curves at different neutron wavelengths. Thus, less diverse lateral structures are present in the spin coated films as compared to the sprayed films. Moreover, the absolute sizes differ between the two deposition methods. In sprayed films the small-sized domains have a size of 30±7 nm and the middle-sized domains a size of 59±9 nm. In contrast, the films prepared via spin coating show significantly smaller domains (size: 27±3 nm). This again proves that the film deposition method makes a substantial difference for the morphology of the hybrid films. The same structure sizes are extracted from the cuts at both, short and long wavelengths. Thus, the morphologies buried in the films are consistent with the surface morphologies for both sprayed and spin coated samples. With respect to the application in HBSCs, the diffusion length scale of excitons generated in P3HT is only about 10 nm.16 Thus, the contribution to exciton separation of the large-sized structure is the least relevant. In contrast, the middle- and small-sized structures make a large contribution to the exciton separation. The smaller and less diverse domain sizes in the spin coated samples are expected to enhance the exciton separation when being used for HBSCs.


15


Page 16 of 27

Figure 6. Horizontal line cuts of the 2D GISANS data for the ZnO/P3HT/P3HT-b-PEO hybrid films deposited by (a) spray coating and (b) spin coating obtained from the 2D GISANS scattering pattern. The solid curves are the fits using the geometry of cylindrical scattering objects on a 1D paracrystal lattice as described in the text. From bottom to top, the average neutron wavelength increases from 0.38 to 1.14 nm. All cuts are shifted along the y axis for clarity.

3.2 Morphology Tuning by Changing ZnO fraction in spray coating. From the direct comparison, the spin coated ZnO/P3HT/P3HT-b-PEO hybrid films are supposed to be superior in the application as HBSCs due to the smaller domain sizes and the larger interface between the ZnO particles and P3HT. However, it is a great challenge to use spin coating for a large-scale industrial film production or on curved surfaces. In contrast, spray deposition seems to be a more powerful method as it can be scaled up towards an industrial style fabrication.45


16

Page 17 of 27 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Moreover, it also shows great promise in depositing materials on curved or even irregular surface. Therefore, it is more significant to optimize the film morphology prepared via spray coating and we investigate to what extend the morphology reached with spin coating can be achieved with spraying as well. Figure 7 shows the surface morphologies of spray coated films for different ratios of wZnO: wP3HT: wP3HT-b-PEO. ZnO particles tend to interconnect with each other to form a foam-like structure in the hybrid films. The polymer shows a similar behavior which results in good pathways for the charge carrier transport to the respective electrodes for application in HBSCs. For the hybrid films with the ratio of wZnO: wP3HT: wP3HT-b-PEO being 1:5:1 (Figure 7a), some small ZnO domains are observed. However, large domains are present as well at the surface due to aggregation of the ZnO particles during the spray coating process. Thus, even though the ZnO ratio is small, the hybrid films prepared via spray coating are still less homogeneous as compared with the spin coated films. When increasing the amount of ZnO (ratio of wZnO: wP3HT: wP3HT-b-PEO being 2:5:1 in Figure 7b), more large domains are observed, which give rise to an increased surfaces roughness as compared with the spin coated samples. This may be associated with a stronger interaction between the ZnO nanoparticles and the hydrogen bonds contributed from the PEO blocks with increasing the concentration of the reactants. A further increase in the ZnO concentration results in an improved interconnectivity of the ZnO domains (Figure 7c). At the highest concentration of ZnO (Figure 7d), most of the PEO domains are saturated with ZnO and a fine grained ZnO network has formed. To investigate the morphology on a micrometer length scale, OM images for these films are shown in Figure S1. Ripples are present at the surface of all sprayed films. Increasing the ratio of ZnO causes a larger surface roughness, which might be due to the increased viscosity in the solution with increasing concentration of the zinc precursor.


17


Page 18 of 27

Figure 7. SEM images of spray coated ZnO/P3HT/P3HT-b-PEO hybrid films with different ratio of wZnO: wP3HT: wP3HT-b-PEO = (a) 1:5:1, (b) 2:5:1, (c) 3:5:1, (d) 4:5:1.

TOF-GISANS measurements are also performed on the sprayed films with different ZnO ratios to explore their inner morphology. Figure S2 shows selected 2D GISANS data (at average neutron wavelength of 0.46 nm) of the sprayed hybrid films with increasing ZnO concentration. When increasing the ZnO concentration, the Yoneda peaks slightly shift to higher scattering angles as marked in the black dashed arrow, which indicates the increasing critical angle αc for the hybrid films. The vertical line cuts along qy=0 (along the vertical arrow in Figure S2a) for the spray coated films with different weight ratios of ZnO are shown in Figure S3. It is clearly observed that the Yoneda peak position, marked by the dashed red line, shifts to larger scattering angles for all samples when increasing the neutron wavelengths. This shift is due to the linear relationship between the critical angle position of the probed material and the neutron wavelength as described in Equation (1). Moreover, when increasing the concentration of ZnO in the hybrid films, the rate of the shift becomes larger. The corresponding detected critical angles are plotted against the


18

Page 19 of 27 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


wavelength as shown in Figure 8a. A line cross (0, 0) is used to fit the experimental data for each sample according to Equation (1). The increasing slope of the lines indicates that the SLD of the materials follows SLDP3HT, SLDPEO < SLD1:5:1 < SLD2:5:1 < SLD3:5:1 < SLD4:5:1 < SLDZnO. Since the theoretical SLD value of ZnO is larger than those of P3HT and PEO, the SLD of the spray coated hybrid films increases with increasing the ratio of ZnO as shown in Figure 8b. Additionally, the film thickness (Figure S4) increases as well when increasing the ratio of ZnO. The large error bars represent the different values measured at different positions due to the very rough surface from ripple patterns. When increasing the concentration of the zinc precursor, the film thickness increases significantly in spite of the constant flow volumes. The higher concentration of the zinc precursor during the sol-gel synthesis results in more metal oxide being deposited for spray coating.

Figure 8. (a) The experimental Yoneda peak positions (the solid squares) of the hybrid films with different weight ratio of wZnO: wP3HT: wP3HT-b-PEO (green: 1:5:1, brown: 2:5:1, dark blue: 3:5:1, and dark yellow: 4:5:1) obtained from the vertical line cuts and the corresponding linear fits (the solid lines). For reference, the expected critical angles of ZnO (black), P3HT (red) and PEO (blue) are shown as lines, respectively. (b) SLD values extracted from the linear fits of the spray coated samples for different concentrations of ZnO.


19


Page 20 of 27

Horizontal line cuts are performed to investigate the lateral structures as depicted in Figure S5. As mentioned above, the same model is used to fit the curves obtained at different neutron wavelengths. Compared with the spin coated samples with two structures fitting the horizontal line cuts, three structures are again required for fitting of the data of all sprayed hybrid films. This is caused by the broad distribution of the domain sizes in sprayed films. The fitted curves (solid orange curves in Figure S5) are in good agreement with the experimental data. For each curve used for fitting the cuts at different wavelengths, the same structure sizes have been used. Therefore, it demonstrates the consistency of surface and inner morphology for all the sprayed samples with different weight ratios. Figure 9 shows the concentration dependence of the middle- and smalldomain sizes of hybrid films. Along increasing the weight ratio of ZnO, both the middle and the small domain sizes increase, indicating a trend of aggregation of the ZnO nanoparticles. This tendency is also consistent with the surface morphology observed in the SEM images. The sprayed film with a ratio of wZnO: wP3HT: wP3HT-b-PEO = 1:5:1 has the small-sized domains being 20±3 nm and middle-sized domains being 43±7 nm. As compared with the other three sprayed samples these are the smallest values. Therefore, the sprayed sample with the ratio of 1:5:1 has the highest benefit for increasing the interface areas between ZnO and P3HT, hence improving the exciton separation in the active layer of HBSCs. In addition, the sample with the ratio of 1:5:1 shows smaller size differences of the middle-sized domains and the small-sized domains as compared with other samples (size of error bars in Figure 9 indicates the size distribution), which results from a better monodispersity of the films having a ratio of 1:5:1. Compared with the morphology of the spin coated samples, although the domain sizes are still more broadly distributed in the spayed films,


20

Page 21 of 27 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


the average size of the small domains can be decreased also in sprayed films, which will be favorable for the exciton separation in HBSCs.

Figure 9. Domain size of the spray coated ZnO/P3HT/P3HT-b-PEO hybrid films with different ratio of wZnO: wP3HT: wP3HT-b-PEO extracted from the fits to the corresponding horizontal line cuts. Squares (black) indicate small-sized structures and circles (red) middle-sized structures. The error bars indicate the size distribution.

4. CONCLUSION In this work, ZnO/P3HT/P3HT-b-PEO hybrid films are successfully fabricated through a simple one pot sol-gel synthesis method in which the zinc precursor is directly incorporated in the PEO blocks instead of having two steps, namely an initial ZnO nanoparticle fabrication followed by the mixing of ZnO and P3HT. In the process, P3HT-b-PEO is used to modify the interfaces of ZnO and P3HT and to avoid aggregation of ZnO and P3HT induced from macrophase seperation when mixing them. The film morphologies obtained via the two most commonly used deposition


21


Page 22 of 27

techniques, namely spray and spin coating, are investigated. Both, the surface and inner morphologies are probed by SEM and TOF-GISANS, respectively. They reveal that the spin coated samples show smaller domains and less diverse domain sizes as compared to the sprayed samples despite the components in the composite solutions being the same. Although the spin coated films show promise in increasing the interface area for exciton separation, it is a great challenge to use spin coating for large-scale fabrication. Spin coating on curved or irregular surface would even be impossible. Therefore, the morphology of sprayed films is refined by changing the weight ratio of ZnO in the sol-gel. For the sprayed films with a ratio of wZnO: wP3HT: wP3HT-b-PEO = 1:5:1, similar small-domain sizes are realized like in the spin coated films. Thus, irrespective of the deposition method, the film morphology can be optimized towards large interface between ZnO and P3HT, which is beneficial for the exciton separation in HBSCs. The surface roughness of the sprayed films remains larger as compared with the spin coated films, which however, might not be disadvantageous for solar cells. Therefore, through this work, we provide some general guidelines as how to tailor the morphology of hybrid films, which plays a crucial role for future application in HBSCs.

Supporting Information Additional experimental results including the parameters of spray deposition; OM images of the hybrid films with different component ratios; TOF-GISANS data and the film thickness of the hybrid films with increasing the ZnO concentration. This material is available free of charge via the Internet at http://pubs.acs.org.


22

Page 23 of 27 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


AUTHOR INFORMATION Corresponding Author *E-mail: [email protected]. Fax: +49 (0)89 289 12473. Tel: +49 (0)89 289 12451. Author Contributions All authors have given approval to the final version of the manuscript. Notes The authors declare no competing financial interest.

ACKNOWLEDGMENT This work was supported by funding from TUM.solar in the context of the Bavarian Collaborative Research Project Solar Technologies Go Hybrid (SolTech), the Excellence Cluster Nanosystems Initiative Munich (NIM), the Center for NanoScience (CeNS) and the International Research Training Group 2022 Alberta/Technical University of Munich International Graduate School for Environmentally Responsible Functional Hybrid Materials (ATUMS). Kun Wang acknowledges the China Scholarship Council (CSC). The authors thank Dr. Yu Tong from Ludwig-MaximiliansUniversität München for helping with the SEM measurements.

REFERENCES 1. Fahmi, A.; Pietsch, T.; Mendoza, C.; Cheval, N. Functional Hybrid Materials. Mater. Today 2009, 12, 44-50. 2. Hoffmann, F.; Cornelius, M.; Morell, J.; Fröba, M. Silica-Based Mesoporous OrganicInorganic Hybrid Materials. Angew. Chem. Int. Ed. 2006, 45, 3216-3251. 3. Hata, E.; Mitsube, K.; Momose, K.; Tomita, Y. Holographic Nanoparticle-Polymer Composites Based on Step-Growth Thiol-ene Photopolymerization. Opt. Mater. Express 2011, 1, 207-222. 4. Sanchez, C.; Julian, B.; Belleville, P.; Popall, M. Applications of Hybrid OrganicInorganic Nanocomposites. J. Mater. Chem. 2005, 15, 3559-3592.


23


Page 24 of 27

5. Sofos, M.; Goldberger, J.; Stone, D. A.; Allen, J. E.; Ma, Q.; Herman, D. J.; Tsai, W.-W.; Lauhon, L. J.; Stupp, S. I. A Synergistic Assembly of Nanoscale Lamellar Photoconductor Hybrids. Nat. Mater. 2009, 8, 68-75. 6. Jia, L.; Zhao, G.; Shi, W.; Coombs, N.; Gourevich, I.; Walker, G. C.; Guerin, G.; Manners, I.; Winnik, M. A. A Design Strategy for the Hierarchical Fabrication of Colloidal Hybrid Mesostructures. Nat. Commun. 2014, 5, 3882: 1-8. 7. Cho, S.; Choi, W. Solid-Phase Photocatalytic Degradation of PVC-TiO2 Polymer Composites. J. Photochem. Photobiol. A 2001, 143, 221-228. 8. Vendamme, R.; Onoue, S.-Y.; Nakao, A.; Kunitake, T. Robust Free-Standing Nanomembranes of Organic/Inorganic Interpenetrating Networks. Nat. Mater. 2006, 5, 494-501. 9. Song, Q.; Cao, S.; Zavala-Rivera, P.; Ping Lu, L.; Li, W.; Ji, Y.; Al-Muhtaseb, S. A.; Cheetham, A. K.; Sivaniah, E. Photo-Oxidative Enhancement of Polymeric Molecular Sieve Membranes. Nat. Commun. 2013, 4, 1918: 1-9. 10. Gómez-Romero, P.; Chojak, M.; Cuentas-Gallegos, K.; Asensio, J. A.; Kulesza, P. J.; Casañ-Pastor, N.; Lira-Cantú, M. Hybrid Organic-Inorganic Nanocomposite Materials for Application in Solid State Electrochemical Supercapacitors. Electrochem. Commun. 2003, 5, 149153. 11. Wang, X.; Kim, K.; Wang, Y.; Stadermann, M.; Noy, A.; Hamza, A. V.; Yang, J.; Sirbuly, D. J. Matrix-Assisted Energy Conversion in Nanostructured Piezoelectric Arrays. Nano Lett. 2010, 10, 4901-4907. 12. Wright, M.; Uddin, A. Organic-Inorganic Hybrid Solar Cells: A Comparative Review. Sol. Energy Mater. Sol. Cells 2012, 107, 87-111. 13. Huynh, W. U.; Dittmer, J. J.; Alivisatos, A. P. Hybrid Nanorod-Polymer Solar Cells. Science 2002, 295, 2425-2427. 14. Liu, Z.; Sun, Y.; Yuan, J.; Wei, H.; Huang, X.; Han, L.; Wang, W.; Wang, H.; Ma, W. High-Efficiency Hybrid Solar Cells Based on Polymer/PbSxSe1-x Nanocrystals Benefiting from Vertical Phase Segregation. Adv. Mater. 2013, 25, 5772-5778. 15. Sun, B.; Snaith, H. J.; Dhoot, A. S.; Westenhoff, S.; Greenham, N. C. Vertically Segregated Hybrid Blends for Photovoltaic Devices with Improved Efficiency. J. Appl. Phys. 2004, 97, 014914: 1-6. 16. Kurrle, D.; Pflaum, J. Exciton Diffusion Length in the Organic Semiconductor Diindenoperylene. Appl. Phys. Lett. 2008, 92, 133306: 1-3. 17. Wang, H.; Wang, H.-Y.; Gao, B.-R.; Wang, L.; Yang, Z.-Y.; Du, X.-B.; Chen, Q.-D.; Song, J.-F.; Sun, H.-B. Exciton Diffusion and Charge Transfer Dynamics in Nano Phase-Separated P3HT/PCBM Blend Films. Nanoscale 2011, 3, 2280-2285. 18. Li, F.; Shi, Y.; Yuan, K.; Chen, Y. Fine Dispersion and Self-Assembly of ZnO Nanoparticles Driven by P3HT-b-PEO Diblocks for Improvement of Hybrid Solar Cells Performance. New J. Chem. 2013, 37, 195-203. 19. Shi, Y.; Li, F.; Chen, Y. Controlling Morphology and Improving the Photovoltaic Performances of P3HT/ZnO Hybrid Solar Cells Via P3HT-b-PEO as an Interfacial Compatibilizer. New J. Chem. 2013, 37, 236-244. 20. Lin, Y.; Wei, Q.; Qian, G.; Yao, L.; Watkins, J. J. Morphology Control in TiO2 Nanorod/Polythiophene Composites for Bulk Heterojunction Solar Cells Using Hydrogen Bonding. Macromolecules 2012, 45, 8665-8673.


24

Page 25 of 27 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


21. Moshonov, M.; Frey, G. L. Directing Hybrid Structures by Combining Self-Assembly of Functional Block Copolymers and Atomic Layer Deposition: A Demonstration on Hybrid Photovoltaics. Langmuir 2015, 31, 12762-12769. 22. Razza, S.; Castro-Hermosa, S.; Di Carlo, A.; Brown, T. M. Research Update: Large-Area Deposition, Coating, Printing, and Processing Techniques for the Upscaling of Perovskite Solar Cell Technology. APL Mater. 2016, 4, 091508: 1-15. 23. Song, L.; Wang, W.; Körstgens, V.; González Daniel, M.; Yao, Y.; Minar Norma, K.; Feckl Johann, M.; Peters, K.; Bein, T.; Fattakhova-Rohlfing, D.; Santoro, G.; Roth, S. V.; MüllerBuschbaum, P. Spray Deposition of Titania Films with Incorporated Crystalline Nanoparticles for All-Solid-State Dye-Sensitized Solar Cells Using P3HT. Adv. Funct. Mater. 2016, 26, 1498-1506. 24. Wang, K.; Bießmann, L.; Schwartzkopf, M.; Roth, S. V.; Müller-Buschbaum, P. Tuning of the Morphology and Optoelectronic Properties of ZnO/P3HT/P3HT-b-PEO Hybrid Films Via Spray Deposition Method. ACS Appl. Mater. Interfaces 2018, 10, 20569-20577. 25. Salditt, T.; Brotons, G. Biomolecular and Amphiphilic Films Probed by Surface Sensitive X-Ray and Neutron Scattering. Anal. Bioanal. Chem. 2004, 379, 960-973. 26. Wolff, M.; Magerl, A.; Zabel, H. Structure of Polymer Micelles Close to the Solid Interface. Eur. Phys. J. E 2005, 16, 141-145. 27. Müller-Buschbaum, P.; Schulz, L.; Metwalli, E.; Moulin, J. F.; Cubitt, R. Lateral Structures of Buried Interfaces in ABA-Type Triblock Copolymer Films. Langmuir 2008, 24, 7639-7644. 28. Kerscher, M.; Busch, P.; Mattauch, S.; Frielinghaus, H.; Richter, D.; Belushkin, M.; Gompper, G. Near-Surface Structure of a Bicontinuous Microemulsion with a Transition Region. Phys. Rev. E 2011, 83, 030401. 29. Kampmann, R.; Haese-Seiller, M.; Kudryashov, V.; Deriglazov, V.; Tristl, M.; Daniel, C.; Toperverg, B.; Schreyer, A.; Sackmann, E. The Potential of the Horizontal Reflectometer Refsans/FRM-II for Measuring Low Reflectivity and Diffuse Surface Scattering. Physica B 2004, 350, E763-E766. 30. Kampmann, R.; Haese-Seiller, M.; Kudryashov, V.; Nickel, B.; Daniel, C.; Fenzl, W.; Schreyer, A.; Sackmann, E.; Rädler, J. Horizontal ToF-Neutron Reflectometer Refsans at FRM-II Munich/Germany: First Tests and Status. Physica B 2006, 385, 1161-1163. 31. Kaune, G.; Haese‐Seiller, M.; Kampmann, R.; Moulin, J. F.; Zhong, Q.; MüllerBuschbaum, P. TOF-GISANS Investigation of Polymer Infiltration in Mesoporous TiO2 Films for Photovoltaic Applications. J. Polym. Sci. Part B: Polym. Phys. 2010, 48, 1628-1635. 32. Das, S.; Yang, B.; Gu, G.; Joshi, P. C.; Ivanov, I. N.; Rouleau, C. M.; Aytug, T.; Geohegan, D. B.; Xiao, K. High-Performance Flexible Perovskite Solar Cells by Using a Combination of Ultrasonic Spray-Coating and Low Thermal Budget Photonic Curing. ACS Photonics 2015, 2, 680-686. 33. Lee, J.-h.; Sagawa, T.; Yoshikawa, S. Morphological and Topographical Characterizations in Spray Coated Organic Solar Cells Using an Additional Solvent Spray Deposition. Org. Electron. 2011, 12, 2165-2173. 34. Deegan, R. D.; Bakajin, O.; Dupont, T. F.; Huber, G.; Nagel, S. R.; Witten, T. A. Capillary Flow as the Cause of Ring Stains from Dried Liquid Drops. Nature 1997, 389, 827-829. 35. Liu, S.; Zhang, X.; Yin, M.; Feng, H.; Zhang, J.; Zhang, L.; Xie, W. Coffee-Ring-Free Ultrasonic Spray Coating Single-Emission Layers for White Organic Light-Emitting Devices and Their Energy-Transfer Mechanism. ACS Appl. Energy Mater. 2018, 1, 103-112. 36. Fukuda, T.; Sato, A. Fluorene Bilayer for Polymer Organic Light-Emitting Diode Using Efficient Ionization Method for Atomized Droplet. Org. Electron. 2015, 26, 1-7.


25


Page 26 of 27

37. Ruderer, M. A.; Guo, S.; Meier, R.; Chiang, H. Y.; Körstgens, V.; Wiedersich, J.; Perlich, J.; Roth, S. V.; Müller-Buschbaum, P. Solvent-Induced Morphology in Polymer-Based Systems for Organic Photovoltaics. Adv. Funct. Mater. 2011, 21, 3382-3391. 38. Hoppe, H.; Sariciftci, N. S. Morphology of Polymer/Fullerene Bulk Heterojunction Solar Cells. J. Mater. Chem. 2006, 16, 45-61. 39. Ruderer, M. A.; Wang, C.; Schaible, E.; Hexemer, A.; Xu, T.; Müller-Buschbaum, P. Morphology and Optical Properties of P3HT:MEH-CN-PPV Blend Films. Macromolecules 2013, 46, 4491-4501. 40. Müller-Buschbaum, P.; Kaune, G.; Haese-Seiller, M.; Moulin, J. F. Morphology Determination of Defect-Rich Diblock Copolymer Films with Time-of-Flight Grazing-Incidence Small-Angle Neutron Scattering. J. Appl. Cryst. 2014, 47, 1228-1237. 41. Müller-Buschbaum, P.; Maurer, E.; Bauer, E.; Cubitt, R. Surface Versus Confinement Induced Morphology Transition in Triblock Copolymer Films: A Grazing Incidence Small Angle Neutron Scattering Investigation. Langmuir 2006, 22, 9295-9303. 42. Rawolle, M.; Sarkar, K.; Niedermeier, M. A.; Schindler, M.; Lellig, P.; Gutmann, J. S.; Moulin, J.-F.; Haese-Seiller, M.; Wochnik, A. S.; Scheu, C.; Müller-Buschbaum, P. Infiltration of Polymer Hole-Conductor into Mesoporous Titania Structures for Solid-State Dye-Sensitized Solar Cells. ACS Appl. Mater. Interfaces 2013, 5, 719-729. 43. Müller-Buschbaum, P.; Metwalli, E.; Moulin, J. F.; Kudryashov, V.; Haese-Seiller, M.; Kampmann, R. Time of Flight Grazing Incidence Small Angle Neutron Scattering. Eur. Phys. J. Spec. Top. 2009, 167, 107-112. 44. Lazzari, R. Isgisaxs: A Program for Grazing-Incidence Small-Angle X-Ray Scattering Analysis of Supported Islands. J. Appl. Crystallogr. 2002, 35, 406-421. 45. Su, B.; Körstgens, V.; Yao, Y.; Magerl, D.; Song, L.; Metwalli, E.; Bernstorff, S.; MüllerBuschbaum, P. Pore Size Control of Block Copolymer-Templated Sol-Gel-Synthesized Titania Films Deposited Via Spray Coating. J. Sol-Gel Sci. Technol. 2017, 81, 346-354.


26

Page 27 of 27 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


TOC figure


27

P3HT-b-PEO Hybrid Films

Recommend Documents