Fabrication and processing of polymer solar cells: A review of printing and coating techniques

Intensive exploration and research in the past few decades on polysaccharide nanocrystals, the highly crystalline nanoscale materials derived from natural resources, mainly focused originally on their use as a reinforcing nanophase in nanocomposites. However, these investigations have led to the emergence of more diverse potential applications exploiting the functionality of these nanomaterials. Based on the construction strategies of functional nanomaterials, this article critically and comprehensively reviews the emerging polysaccharide nanocrystal-based functional nanomaterials with special applications, such as biomedical materials, biomimetic optical nanomaterials, bio-inspired mechanically adaptive nanomaterials, permselective nanostructured membranes, template for synthesizing inorganic nanoparticles, polymer electrolytes, emulsion nano-stabilizer and decontamination of organic pollutants. We focus on the preparation, unique properties and performances of the different polysaccharide nanocrystal materials. At the same time, the advantages, physicochemical properties and chemical modifications of polysaccharide nanocrystals are also comparatively discussed in view of materials development. Finally, the perspective and current challenges of polysaccharide nanocrystals in future functional nanomaterials are outlined.

Preparation, properties and applications of polysaccharide nanocrystals in advanced functional nanomaterials: a review

The improvement of the performance of roll-to-roll processed polymer solar cell modules through miniaturization of the device outline is described. The devices were prepared using full roll-to-roll processing comprising flexographic printing, slot-die coating and rotary screen printing to create 5 mm wide lines of ZnO, P3HT:[60/70]PCBM, PEDOT:PSS and silver on an ITO-PET substrate. The lines were spaced by 1 mm and the devices were completed by encapsulation using roll-to-roll lamination on both sides using a pressure sensitive adhesive and a multilayered barrier material having a UV-filter with a cut-off at 390 nm, oxygen and water vapor transmission rates of respectively 0.01 cm3 m−2 bar−1 day−1 and 0.04 g m−2 day−1. The final modules comprised 16 serially connected cells. The technical yield was 89% based on the criterion that the Voc had to be larger than 7.2 V. This set of modules gave respectively a voltage, current, fill factor and power conversion efficiency of 8.47 ± 0.41 V, −23.20 ± 4.10 mA, 35.4 ± 2.8% and 1.96 ± 0.34% in the case of modules based on P3HT:[60]PCBM. A total of 1960 modules were prepared for each run and the best power conversion reached was 2.75% for devices based on P3HT:[70]PCBM. The solar cell modules were used to demonstrate the complete manufacture of a small lamp entirely using techniques of flexible electronics. The solar cell module was used to charge a polymer lithium ion battery through a blocking diode. The entire process was fully automated and demonstrates the capacity of polymer solar cells in the context of flexible and printed electronics. Finally a comparison was made between the learning curve for OPV and crystalline silicon solar cells in terms of the cost per watt peak and the cumulative watt peak. OPV as a technology was found to have a significantly steeper learning curve.

Product integration of compact roll-to-roll processed polymer solar cell modules: methods and manufacture using flexographic printing, slot-die coating and rotary screen printing

The development of surfaces that have switchable properties, also known as smart surfaces, have been actively pursued in the past few years. The recent surge of interest in these switchable systems stems from the widespread number of applications to many areas in science and technology ranging from environmental cleanup to data storage, micro- and nanofluidic devices. Moreover, the ability to modulate biomolecule activity, protein immobilisation, and cell adhesion at the liquid–solid interface is important in a variety of biological and medical applications, including biofouling, chromatography, cell culture, regenerative medicine and tissue engineering. Different materials have been exploited to induce such changes in surface biological properties that are mostly based on self-assembled monolayers or polymer films. This critical review focuses on the recent progress in the preparation of these switchable surfaces, and highlights their applications in biological environments. The review is organized according to the external stimuli used to manipulate the properties of the substrate—chemical/biochemical, thermal, electric and optical stimuli. Current and future challenges in the field of smart biological surfaces are addressed (189 references).

Stimuli-responsive surfaces for bio-applications.

Biological membranes play an essential role in living organisms by providing stable and functional compartments, preserving cell architecture, whilst supporting signalling and selective transport that are mediated by a variety of proteins embedded in the membrane. However, mimicking cell membranes – to be applied in artificial systems – is very challenging because of the vast complexity of biological structures. In this respect a highly promising strategy to designing multifunctional hybrid materials/systems is to combine biological molecules with polymer membranes or to design membranes with intrinsic stimuli-responsive properties. Here we present supramolecular polymer assemblies resulting from self-assembly of mostly amphiphilic copolymers either as 3D compartments (polymersomes, PICsomes, peptosomes), or as planar membranes (free-standing films, solid-supported membranes, membrane-mimetic brushes). In a bioinspired strategy, such synthetic assemblies decorated with biomolecules by insertion/encapsulation/attachment, serve for development of multifunctional systems. In addition, when the assemblies are stimuli-responsive, their architecture and properties change in the presence of stimuli, and release a cargo or allow “on demand” a specific in situ reaction. Relevant examples are included for an overview of bioinspired polymer compartments with nanometre sizes and membranes as candidates in applications ranging from drug delivery systems, up to artificial organelles, or active surfaces. Both the advantages of using polymer supramolecular assemblies and their present limitations are included to serve as a basis for future improvements.

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Bioinspired polymer vesicles and membranes for biological and medical applications

Spin-coating is widely employed for the highly reproducible fabrication of thin film coatings over large areas with high structural uniformity. Research in recent years has extended the scope of spin-coating by chemically engineering the interface of support and solution to obtain specific structural order in the resulting supported thin films. This review will discuss both the fundamental physical and chemical processes governing the conventional spin-coating process and describe methodologies for the preparation of spin-coated polymer thin films. Furthermore, a range of advanced applications and recent developments within this field will be reviewed with focus on engineering chemical and topological structure during the coating process.

K. Norrman

Papers

6 Studies of spin-coated polymer films