Self‐Organization of Ink‐jet‐Printed Triisopropylsilylethynyl Pentacene via Evaporation‐Induced Flows in a Drying Droplet

Abstract

We have demonstrated the influence of evaporation‐induced flow in a single droplet on the crystalline microstructure and film morphology of an ink‐jet‐printed organic semiconductor, 6,13‐bis((triisopropylsilylethynyl) pentacene (TIPS_PEN), by varying the composition of the solvent mixture. The ringlike deposits induced by outward convective flow in the droplets have a randomly oriented crystalline structure. The addition of dichlorobenzene as an evaporation control agent results in a homogeneous film morphology due to slow evaporation, but the molecular orientation of the film is undesirable in that it is similar to that of the ring‐deposited films. However, self‐aligned TIPS_PEN crystals with highly ordered crystalline structures were successfully produced when dodecane was added. Dodecane has a high boiling point and a low surface tension, and its addition to the solvent results in a recirculation flow in the droplets that is induced by a Marangoni flow (surface‐tension‐driven flow), which arises during the drying processes in the direction opposite to the convective flow. The field‐effect transistors fabricated with these self‐aligned crystals via ink‐jet printing exhibit significantly improved performance with an average effective field‐effect mobility of 0.12 cm2 V–1 s–1. These results demonstrate that with the choice of appropriate solvent ink‐jet printing is an excellent method for the production of organic semiconductor films with uniform morphology and desired molecular orientation for the direct‐write fabrication of high‐performance organic electronics.

Large-area formation of self-aligned crystalline domains of organic semiconductors on transistor channels using CONNECT

“…S7). In comparison, other patterning methods used to create patterned OSCs for isolated OTFTs have shown relative variances ranging from 20% to 84% (9,15,17,22,31,32,35,42,(48)(49)(50)(51)(52)(53)(54). For example, Li et al (15) have shown that using a PMMA:C8BTBT blend on a solution wetting pattern can deposit crystal plates that have a mobility relative variance of >40%.…”

Control of the Particle Distribution in Inkjet Printing through an Evaporation-Driven Sol–Gel Transition

“…Thermal Marangoni flows may arise on heated/cooled substrates, 27,28 or through evaporative cooling. 32,35 Alternatively, solutal Marangoni flows can occur in solvent mixtures, 15,23,36,37 or in the presence of surfactants. 24,38,39 However, when the droplet becomes thin, the evaporation-driven capillary flow may overcome the Marangoni flow, producing a ring stain.…”

Organic semiconductors for device applications: current trends and future prospects

“…Next, the organic molecules in the channel region must be appropriately organized to ensure the optimal charge carrier transport. Here, proper molecular design, improved self-alignment through surface modification, and thermal annealing all help to enhance the orbital overlap leading to improved charge carrier hopping [112][113][114][115][116]. Subsequently, the dielectric film used must provide the maximum capacitance, which is possible either using high dielectric constant material or reducing the dielectric film thickness.…”