Determination of the Ordered Structure in Conjugated-Coil Diblock Copolymers Films from a Thickness Gradient Prepared by Spin-Coated Drop Technique

Abstract

Investigating the thickness dependence of ordered structure of thin films of electrically conducting conjugated polymers with nano-ordered morphologies is essential for optimizing their applications in advanced electrooptic devices. We demonstrate here that by spin-coating a small drop of a conjugated-coil diblock copolymer, a thickness gradient varying between tens of nanometers to a few micrometers is formed at the drop rim. Compared to other widely used solution casting methods for the preparation of thickness gradients, the spin-coated drop technique produces film gradients with thickness in the interesting range for most applications in an extremely short preparation time. Using a submicrometersized X-ray beam and a scanning technique, spatial mappings of the gradient area are obtained with submicrometer grazing incidence small-angle X-ray scattering (sub-μGISAXS) for the first time. Investigating the thickness gradient with sub-μGISAXS has the advantage of saving the preparations and investigations of many samples each with a certain thickness under identical conditions. As a model system, we use the diblock copolymer polystyrene-block-poly( p-phenylene) with a thickness gradient ranging between 80 and 2280 nm. Detailed analysis of the scattering patterns at selected positions along the gradient identifies a regime of lateral order within a thickness range of 80-210 nm.

Determination of the local gold contact morphology on a photoactive polymer film using nanobeam GISAXS

“…As a consequence, a densely packed micellar film is installed, which perfection in packing depends on the actual film thickness. As reported in reference [65] a very small film thickness of 82 nm gives rise to a moderate defined packing. In the horizontal cuts shown in Fig.…”

“…Each micelle is made of a dense PPP core surrounded by a PS shell. As determined recently, such micelles are forming in the toluene solution and maintain the spin coating [65]. As a consequence, a densely packed micellar film is installed, which perfection in packing depends on the actual film thickness.…”

Solvent‐Induced Morphology in Polymer‐Based Systems for Organic Photovoltaics

“…To fit the geometry introduced by thin‐film systems of use for organic photovoltaics, scattering experiments have to be performed in grazing‐incidence geometry. However, only recently studies of the structure of active layers for photovoltaic applications using X‐ray and neutron‐scattering methods have been published 6, 25–30. Reflectivity measurements revealed the vertical material composition, e.g., of poly(3‐hexylthiophene):PCBM (P3HT:PCBM) films which exhibited enrichment layers at the surface and bottom interface 25, 26.…”

Grazing incidence wide angle x-ray scattering at the wiggler beamline BW4 of HASYLAB

“…[14][15][16][17][18][19][20][21][22] For example, thin films for application in organic photovoltaics are formed by photoactive polymers and block copolymers as well as blends of photoactive polymers arranged in functional multilayered systems. [23][24][25] Recently, we investigated the morphology of nanostructured titania thin films for hybrid photovoltaic devices including single titania thin films up to functional multilayer stacks present in real devices with GISAXS at beamline BW4. [26][27][28][29][30][31][32] Besides, the morphological properties of these material systems, most of their possible applications are defined by physical characteristics of electrical, optical, or mechanical nature.…”