Conjugated Polymers Via Direct Arylation Polymerization in Continuous Flow: Minimizing the Cost and Batch-to-Batch Variations for High-Throughput Energy Conversion.

Continuous flow methods are utilized in conjunction with direct arylation polymerization (DArP) for the scaled synthesis of the roll-to-roll compatible polymer, poly[(2,5-bis(2-hexyldecyloxy)phenylene)-alt-(4,7-di(thiophen-2-yl)-benzo[c][1,2,5]thiadiazole)] (PPDTBT). PPDTBT is based on simple, inexpensive, and scalable monomers using thienyl-flanked benzothiadiazole as the acceptor, which is the first ß-unprotected substrate to be used in continuous flow via DArP, enabling critical evaluation of the suitability of this emerging synthetic method for minimizing defects and for the scaled synthesis of high-performance materials. To demonstrate the usefulness of the method, DArP-prepared PPDTBT via continuous flow synthesis is employed for the preparation of indium tin oxide (ITO)-free and flexible roll-coated solar cells to achieve a power conversion efficiency of 3.5% for 1 cm2 devices, which is comparable to the performance of PPDTBT polymerized through Stille cross coupling. These efforts demonstrate the distinct advantages of the continuous flow protocol with DArP avoiding use of toxic tin chemicals, reducing the associated costs of polymer upscaling, and minimizing batch-to-batch variations for high-quality material.

High-Volume Processed, ITO-Free Superstrates and Substrates for Roll-to-Roll Development of Organic Electronics.

The fabrication of substrates and superstrates prepared by scalable roll-to-roll methods is reviewed. The substrates and superstrates that act as the flexible carrier for the processing of functional organic electronic devices are an essential component, and proposals are made about how the general availability of various forms of these materials is needed to accelerate the development of the field of organic electronics. The initial development of the replacement of indium-tin-oxide (ITO) for the flexible carrier materials is described and a description of how roll-to-roll processing development led to simplification from an initially complex make-up to higher performing materials through a more simple process is also presented. This process intensification through process simplification is viewed as a central strategy for upscaling, increasing throughput, performance, and cost reduction.

Aqueous processing of low-band-gap polymer solar cells using roll-to-roll methods.

Aqueous nanoparticle dispersions of a series of three low-band-gap polymers poly[4,8-bis(2-ethylhexyloxy)benzo(1,2-b:4,5-b')dithiophene-alt-5,6-bis(octyloxy)-4,7-di(thiophen-2-yl)(2,1,3-benzothiadiazole)-5,5'-diyl] (P1), poly[(4,4'-bis(2-ethylhexyl)dithieno[3,2-b:2',3'-d]silole)-2,6-diyl-alt-(2,1,3-benzothiadiazole)-4,7-diyl] (P2), and poly[2,3-bis-(3-octyloxyphenyl)quinoxaline-5,8-diyl-alt-thiophene-2,5-diyl] (P3) were prepared using ultrasonic treatment of a chloroform solution of the polymer and [6,6]-phenyl-C(61)-butyric acid methyl ester ([60]PCBM) mixed with an aqueous solution of sodium dodecylsulphate (SDS). The size of the nanoparticles was established using small-angle X-ray scattering (SAXS) of the aqueous dispersions and by both atomic force microscopy (AFM) and using both grazing incidence SAXS (GISAXS) and grazing incidence wide-angle X-ray scattering (GIWAXS) in the solid state as coated films. The aqueous dispersions were dialyzed to remove excess detergent and concentrated to a solid content of approximately 60 mg mL(-1). The formation of films for solar cells using the aqueous dispersion required the addition of the nonionic detergent FSO-100 at a concentration of 5 mg mL(-1). This enabled slot-die coating of high quality films with a dry thickness of 126 ± 19, 500 ± 25, and 612 ± 22 nm P1, P2, and P3, respectively for polymer solar cells. Large area inverted polymer solar cells were thus prepared based on the aqueous inks. The power conversion efficiency (PCE) reached for each of the materials was 0.07, 0.55, and 0.15% for P1, P2, and P3, respectively. The devices were prepared using coating and printing of all layers including the metal back electrodes. All steps were carried out using roll-to-roll (R2R) slot-die and screen printing methods on flexible substrates. All five layers were processed using environmentally friendly methods and solvents. Two of the layers were processed entirely from water (the electron transport layer and the active layer).