Embodied Energy Investigation of the Chloro-Boron Subphthalocyanine Formation Process to Improve Its Sustainability

Chloro-boron subphthalocyanine (Cl-BsubPc) is a representative within the phthalocyanine space and is an organic semiconductor that has been applied as an active material in organic photovoltaics (OPVs). Past work has been done to design a synthetic process that is well-suited for reaction scale-up of a BsubPc. This study investigates the life cycle implications of the established Cl-BsubPc synthetic process from an embodied energy standpoint. The embodied energy of the baseline process is modeled as 7929 MJ/kg-Cl-BsubPc using a cumulative energy demand (CED) methodology. The reaction solvent 1,2-dichlorobenzene is identified as the largest contributor to the total embodied energy with a specific CED of 2513 MJ/kg. Alternative aromatic solvents with lower embodied energies were identified from established databases and tested as drop-in replacements for 1,2-dichlorobenzene. A kinetic study was then conducted to investigate the optimal reaction time of several solvents. 2,4-Dichlorotoluene, with a specific CED of 64 MJ/kg, was found to be a viable alternative to 1,2-dichlorobenzene. Cl-BsubPc made from this new process was then incorporated into OPVs, and the device performance was compared to past baseline devices using Cl-BsubPc made from 1,2-dichlorobenzene. The performance was the same, further justifying the adoption of 2,4-dichlorotoluene in the synthesis of Cl-BsubPc and others.