Indoline as electron donor unit in "push-Pull" organic small molecules for solution processed organic solar cells: Effect of the molecular π-bridge on device efficiency

In this work we have synthesized and characterized four indoline-based small organic molecules for their use as electron donor moiety in bulk-heterojunction solution processed organic solar cells combined with PC₇₀BM as electron acceptor. Our results show a wide range of light to energy efficiencies from 0.8% to 3.5% under standard measurement conditions. An initial analysis suggests that the main limitation is the device photocurrent due to the device film thickness. Yet, charge transfer dynamics were studied to correlate charge loss mechanisms to π-bridge structural variations and, moreover, mobility measurements were also carried out to fully explain these device limitations.