Toward Low-Cost, High-Efficiency, and Scalable Organic Solar Cells with Transparent Metal Electrode and Improved Domain Morphology

We review our recent progress toward realizing future low-cost, high-efficiency, and scalable organic solar cells (OSCs). First, we show that the transparent electrodes based on metallic nanostructure is a strong candidate as a replacement of conventional indium tin oxide (ITO) electrode due to their superior properties, such as high optical transparency, good electrical conductivity, and mechanical flexibility, and the versatility that these properties can be adjusted independently by changing the linewidth and thickness of the metal grid structure. Furthermore, we exploited the unique optical properties due to the excitation of surface plasmon resonance by the metallic nanogratings to enhance the light absorption of organic semiconductors, and demonstrated enhanced power conversion efficiency than devices made using ITO electrode. In addition, we also investigated a new device fabrication process with a focus on the photoactive layer formation, which produces the most optimum bulk-heterojunction morphology compared with conventional annealing-based methods. Finally, we successfully demonstrated that these approaches are scalable to large-area and high-speed roll-to-roll processes. We believe that the works highlighted in this paper represent one step forward to realizing low-cost, high-efficiency, and large-area OSCs.