Roll-to-roll processing system for transparent organic solar cells designed and verified

As an alternative to classical semiconductor-based systems, organic photovoltaic cells use polymers or similar organic molecules to produce electrons that are then carried away through a transparent conductor, such as indium tin oxide. Organic photovoltaics are potentially less expensive than conventional photovoltaics and can be made fully transparent, opening applications that are complementary to classical semiconductor photovoltaic devices. However, they have lower efficiencies, and progress is needed for manufacturing scale production.

New research describes a scalable roll-to-roll process that enables high-yield, single or multiple junction organic photovoltaics. The process uses vacuum thermal evaporation in conjunction with low-pressure organic vapor deposition on a continuously rolling substrate. The raw materials are vaporized and deposited on the substrate in separate, interconnected chambers to create customized recipes that use materials compatible with the molecular vaporization process.

Devices fabricated using the roll-to-roll process had efficiencies of 8.6 and 8.9 percent for single junction and tandem organic photovoltaics, respectively. While these values are well below classical semiconductor-based devices, such as silicon at approximately 20-25 percent, they are comparable with state-of-the-art lab-scale organic cells, suggesting this process can create high-quality and production-scalable devices.

This process has the potential to enable organic photovoltaics to be a cost competitive technology for building applied and building integrated applications such as power-generating windows through high-yield, transparent, color-tunable and quality devices.

Source: “Continuous roll-to-roll fabrication of organic photovoltaic cells via interconnected high-vacuum and low-pressure organic vapor phase deposition systems,” by Boning Qu and Stephen R. Forrest, Applied Physics Letters (2018). The article can be accessed at https://doi.org/10.1063/1.5039701 .