Elastomeric Indoor Organic Photovoltaics with Superb Photothermal Endurance

Abstract

Despite recent improvements in their power-conversion efficiency (PCE), organic photovoltaics (OPVs) cannot yet be guaranteed stable in an indoor environment. In this study, the destabilizing effects of morphological evolution and molecular-ordering variation on photoactive layers containing two to four photoactive components are investigated under realistic indoor photothermal (>55 degrees C for 1000 h) and mechanical (10% strain and 1000 cycles) deformation conditions. Layers with more stable morphologies are obtained by increasing the number of photoactive components; consequently, the quaternary OPVs show the best PCE retention (over 90% and 82% of the initial values after the photothermal and mechanical stresses, respectively). The increase in entropy caused by the additional components in the quaternary blend leads to a more balanced molecular arrangement and excellent photothermal stability. Stronger intermolecular bonding and less variation of molecular ordering likewise occur in the quaternary OPVs, enhancing their mechanical endurance.