A commonly used strategy in the fabrication of organic electronics involves the use of orthogonal solvents, i.e. the alternating use of organic solvents and water for the application of consecutive layers to prevent dissolution of previous layers. This strategy therefore requires the deposition of sequential layers with a large mismatch in surface energy. In case of organic photovoltaics (OPV) a particularly challenging deposition is that of the aqueous Poly(3,4-ethylenedioxythiophene) Polystyrene sulfonate (PEDOT:PSS) on the hydrophobic Poly(3-hexylthiophene-2,5-diyl/Phenyl-C61-butyric acid methyl ester (P3HT/PCBM) layer. The mismatch in surface energy causes dewetting and inhomogeneous layer formation. In inkjet printing individually placed droplets should spread sufficiently far to form a homogeneous closed layer before the solvents in the droplet evaporate. A formulation for the aqueous PEDOT:PSS layer has been developed in which the combination of solvents and surfactants is essential for achieving a homogenous layer on the timescales needed for inkjet printing. Homogenous layers of PEDOT:PSS on P3HT/PCBM were achieved for layer thicknesses from 400 nm to 50 nm. The efficiency of the OPV's fabricated with the new formulation were comparable with reference devices, where evaporated molybdenum oxide (MoOx) was used as a topelectrode. This shows that by the addition of solvents and surfactants a hydrophilic solution can be inkjet printed successfully to form homogenous layers on hydrophobic surfaces and achieve good efficiencies in an inverted organic solar cell.@en

The large volume production of flexible electronics by solution based roll-to-roll (R2R) manufacturing technologies is a promising upscaling strategy for the organic electronics industry. Typical optoelectronic devices like organic light emitting diodes (OLEDs) consist of a complex stack of functional layers. Solution deposition of these structures eliminates the need for expensive vacuum processing. This contribution presents approaches for solution based R2R production methods of functional OLED layers on flexible polymer substrates. The development of a R2R line with two slot-die coating stations is discussed which can deposit two uniform layers consecutively in a single run (“tandem coating”) at web speeds up to 30 m/min. Furthermore, it offers the unique feature that there is no contact between the rollers and the top side of the substrate where the functional coating is deposited. Thereby, an important source of particle contamination and other damage to the device is eliminated. In addition to continuous deposition, stripe and intermittent coating techniques have been developed, allowing the production of patterned layers. Finally, examples will be shown of OLEDs where two functional materials are deposited by R2R processing from solution.@en

Current laboratory-scale fabrication of perovskite solar cells involves the use of toxic solvents in the different fabrication steps. The aim of this research is to find a nontoxic alternative to chlorobenzene used for the deposition of hole transport material (HTM) spiro-OMeTAD. The initial selection of the solvents compatible with industrial manufacturing was performed based on the Hansen solubility model and further verified in a series of solubility tests, because the additives used in the HTM ink, such as lithium bis(trifluoromethanesulfonimidate) (Li-TFSI) and tert-butylpyridine (4-TBP), also have a significant influence on the properties of the final solution. Furthermore, selected solvents were tested on the compatibility with the underlying perovskite layer, which should remain unaffected after the spiro-OMeTAD deposition. A final selection of solvents was tested by the manufacturing of the complete perovskite solar cells. Power conversion efficiency (PCE) and layer quality, as well as possible health issues and environmental concerns, influenced the final selection for future potential industrial processing. The research demonstrated that replacement of chlorobenzene (CB) by p-xylene leads to identical PCEs of the devices, thereby showing that a toxic solvent can be replaced by a nontoxic and industrially compatible one. To prove that the selected solvent is suitable for future large-area coatings, the coatability of the ink was tested in blade-coating deposition. Devices manufactured using blade coating demonstrated identical PCEs to spin-coated devices, which is final proof of the suitability of the selected solvent system.@en

The feasibility of upscaling the perovskite solar cells technologies to high volume production using roll-to-roll (R2R) slot die coating is demonstrated in this study. Perovskite solar cells are produced by R2R slot die coating on flexible substrates with a width of 30 cm and the web speed of 3–5 m min−1. R2R deposition of the electron transport layer and perovskite is performed at ambient atmosphere from nontoxic solvents compatible with industrial manufacturing. The average stabilized power conversion efficiency of the devices made on different areas of the foil is 12%, with the best value of 13.5%. The demonstrated achievement is an important milestone and a big solid step toward future commercialization of perovskite-based solar cells technologies.@en