Abstract: Organic solar cells (OSCs) employ semi-transparent active layers deposited through solution processes. Combining these low-cost active layers with transparent electrodes, one can produce smart windows that harvest energy from the sun. To fulfill their role as energy source for sustainable urban designs, OSC-based photovoltaic windows have to overcome major drawbacks such as reducing materials and hazardous solvent wastes generated during active layer fabrication. Additionally, to replace conventional windows, the photovoltaic windows should transmit enough visible light and avoid having a colored-glass aspect which would change the spectrum of the transmitted light.

Here, we demonstrate that employing ternary active layers (three active materials) can simultaneously increase the photovoltaic performances and optical properties of light-harvesting windows. Following this strategy, we fabricated efficient neutral color photovoltaic windows with a color rendering index and an average visible transparency over 95 and 40%, respectively. Furthermore, to increase the sustainability and environment-friendliness of their production, we developed a new thin film fabrication process called push-coating. Using push-coating, uniform thin films that generate similar photovoltaic performances to spin-coated ones can be fabricated with no material waste and 20 times less hazardous solvents than with spin-coating.

Our results thus open the path to extremely low-cost and eco-friendly fabrication of innovative photovoltaic technologies which could strongly impact the global energy roadmap.



Keywords: Organic Solar Cells, Green & Sustainable Fabrication, Emerging Photovoltaic Technology.

[1] Sano et al. ACS Applied Energy Materials 2, 2534-2540 (2019)
[2] Inaba et al. ACS Applied Materials & Interfaces 11, 10785-10793 (2019)
[3] Vohra et al. ACS Applied Materials & Interfaces 9, 25434-25444 (2017)

Biography: Dr. Varun Vohra is a French researcher with Indian origins who received his PhD in Materials Science from the University of Milan-Bicocca in Italy in 2009. He was selected as EU Marie-Curie Fellow (2006-2009) and was awarded two prestigious JSPS Fellowships (2011-2012 and 2012-2014) for his studies on organic solar cells (OSCs). He joined the University of Electro-Communications in Tokyo in 2014 and has since developed his knowledge of organic semiconductors and OSCs. He is one of the pioneer researchers who successfully fabricated OSCs with power conversion efficiencies over 10% and his group now focuses on developing sustainable solutions for OSC fabrication. He has published numerous academic contributions on prestigious journals such as Nature Photonics and has been awarded the NF Foundation and IAAM Lecture Awards in 2019.