Understanding Marangoni flow-driven solidification of polymer semiconducting films on an aqueous substrate†
Here, in the context of the polymer film on an aqueous transfer process, the value of spreading coefficient (S) plays an important role in spreading the polymer solution droplet on the base media. A high S is key to improving the polymer film uniformity and crystalline structure, which affect the organic field-effect transistor (OFET) device performance. In addition, the films floating on the base media were transferred either upward (UST) or downward (BST) to differ their solidified orientations. The differences between the UST and BST cases confirmed that the solvent in the polymer solution droplet was rapidly extracted at the interface with the base media and was slowly evaporated near the air interface with the polymer solution. The results induce rapid solidification with poor structural properties at the base media interface and slow solidification with good structural properties at the air interface. The surface properties of the polymer semiconducting films were advantageous in the vicinity of the air/polymer solution interfaces for use as a channel active layer, resulting in good OFET device performances for the UST case.