“Buried” nano-structure and molecular aggregation state in ordered heterojunction poly(3-hexylthiophene)-based photovoltaics

Abstract

The morphology of ordered heterojunction organic photovoltaics (OHJ-OPVs) interfaces was evaluated using synchrotron radiation small angle X-ray scattering and grazing incidence X-ray diffraction. [6,6$]-phenyl C61-butyric acid methyl ester (PCBM) was deposited on the line/space patterned poly(3-hexylthiophene-2,5-diyl) (P3HT) thin film fabricated by nano-imprinting. After deposition of the PCBM film, the P3HT thin film retained the rectangular edge features of the imprinted mold, with some Gaussian broadening due to interdiffusion and partial phase mixing at the P3HT/PCBM interface. The P3HT main chains were oriented vertically in the nano-imprinted line pattern and showed π-π stacking along the line direction. PCBM nano-crystals exist throughout the OHJ-OPV thin film.

Large Molecular Weight Polymer Solar Cells with Strong Chain Alignment Created by Nanoimprint Lithography

“…The chain alignment of nonimprinted thin films and imprinted P3HT nanogratings with various MWs as listed in Table are studied using GIXRD (Rigaku Ultima III diffractometer). According to literature studies, the edge-on configuration is the dominant chain orientation in flat P3HT thin films, and it changes to vertical orientation in imprinted nanostructures. ,− The edge-on and vertical orientations can be properly analyzed using two kinds of GIXRD configurations, i.e., out-of-plane and in-plane, respectively. As shown in Figure a1,a2, in the out-of-plane GIXRD, the detector is rotated vertically with respect to the P3HT surface with a scan axis of 2θ, so that the strong vertical diffraction signals from the large polymer backbones with spacing a in edge-on orientation can be collected.…”

Molecular aggregation states and wetting behavior of a poly{2-(perfluorooctyl)ethyl acrylate} brush-immobilized nano-imprinted surface

“…The pillar diameter is enlarged as a result of the PFA-C 8 grafting, and the PFA-C 8 grafting layer thickness is roughly estimated to be about 20e30 nm. It should be noted that the lateral morphology is inaccurate in the AFM observation due to the convolution of the tip shape with the surface morphologies [32]. The concave region would be rapidly filled with polymer brushes because of the chain growth in both the pillar side and the concave ground walls, leading to a reduction of the height contrast.…”

“…GIXD affords not only the bulk structure but also the outermost surface structure, depending on the incident angle (a i ) of the X-ray [32,33]. The incident X-ray is totally reflected and penetrates into the thin films as an evanescent wave when a i is smaller than the critical angle (a c ).…”

Depth-Resolved Characterization of Perylenediimide Side-Chain Polymer Thin Film Structure Using Grazing-Incidence Wide-Angle X-ray Diffraction with Tender X-rays

“…Surface analytical measurements including grazing-incidence wide-angle X-ray diffraction (GIWAXD), X-ray photoelectron spectroscopy, , time-of-flight secondary ion mass spectrometry, , and neutron reflectivity are widely utilized in various fields. Among them, GIWAXD has the advantage of determining the distribution of not only the ordered structures but also the buried interfaces in thin films along the thickness direction . Meanwhile, the refractive index of polymeric materials is generally higher than that of air, and for X-rays, the value is slightly lower than that of air.…”

“…Among them, GIWAXD has the advantage of determining the distribution of not only the ordered structures but also the buried interfaces in thin films along the thickness direction. 22 Meanwhile, the refractive index of polymeric materials is generally higher than that of air, and for X-rays, the value is slightly lower than that of air. Subsequently, the evanescent wave is generated when the X-ray beam is irradiated from the air to the polymer surface below the critical angle, α c .…”