Spin-coated inks

The donor-acceptor components should be the suitable phase size to allow the maximum p-n interface for charge generation. This will allow all excitons transfer to p-n interface and effective charge tfansport in the bicontinuous pathway to the electrodes to minimize the recombination of free charges. The morphology of the active layer depends on the interplay between the material property and device fabrication, such as the solvent used, overall concentration of the blend component, deposition technique (spin coating, ink-jet printing, roll-to-roll, etc.), solvent evaporation rate, and temperature. 

Although spin coated OTFTs with PQT-12 semiconductors have high mobility and on/off ratio characteristics, the performance of those fabricated by inkjet patterning is more variable. This may be attributable to the tendency of PQT-12 solution to gel at room temperature, leading to nonuniformity in the jetted semiconductor channel layers. This deficiency of the PQT solution as an inkjet ink is expected to be a practical challenge in manufacture, and must therefore be addressed. By study of the solution behavior of PQTs, we have subsequently developed a nanoparticle dispersion of PQT-12, which effectively resolves this challenging problem (vide infra). 

The ability to provide more processable inherently conducting polymers, as described above, enables new approaches to device fabrication, including ink jet printing [153] and screen printing [154]. Photolithography has also been used to produce ICP patterns [155-157], while spin coating has been used to produce thin, even films [158]. 

Soft lithography The pattern-transfer element is formed by pouring a liquid polymer onto a master made from silicon. This replica can be used as a stamp to transfer chemical ink, such as a solution of alkanethiol, to a surface. Spin-coating Thin film formation by deposition of a solution onto a solid, which is then rotated at a speed of several thousand revolutions per minute. 

The polymer is commonly applied by spin-coating or ink-jet printing, while the electrodes are usually constructed by vacuum deposition or sputtering. In this sequential fabrication process, both wet processes and dry processes are required. 

Surface morphology of films was measured by the optical interferogram (Wyko) of 60 p,m x 45.5 p,m area. For comparison, formulated ink was spin-coated on a glass substrate with the same thickness of 220 mn, which is similar to that of an inkjet-printed layer. No pin-holes were observed on layers deposited using either techniques. However, in both cases, many randomly positioned voids have been observed on the dried PEDOT-PSS surface. Figure 3.9a shows the surface of the inkjet-printed film... 

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