A mini-slot die coater: bridging the gap between the laboratory and processing line

 
Characterizing materials in real time and in situ on a processing line can be a challenge and expensive when materials are under development, since large quantities of materials are required. Translating laboratory results, obtained under "academic" conditions, to the processing line can be dangerous. We have developed a potential solution to this dilemma and we use the fabrication of organic photovoltaic films as an example. Polymer-based materials for harvesting solar energy hold promise to reduce fabrication costs and increase flexibility of efficient photovoltaic devices. Most efforts have focused on lab-scale devices where spin-coating has been used to fabricate high performance devices, a process that is not amenable to large scale fabrication. This mismatch in device fabrication processes makes it difficult to translate quantitative results obtained from laboratory scale devices to commercially prepared large area devices, making optimization difficult. Using a mini-slot die coater, we address this issue, where the commercial process is translated to the laboratory setting and sophisticated characterization tools are used in real time and in situ to characterize the active layer of polymer-based devices as films are cast from solution. The evolution of the morphology in the active layer is characterized under different drying conditions and we propose a mechanism by which the morphology in the dried film is produced. This mini-slot die coater offers a simple, convenient, materials efficient route by which the morphology in the active layer can be optimized. In addition, the mii-slot die coater is amenable to roll-to-roll processing wherein on-line characterization of the development of the morphology can be realized.