Revealing electron transport connectivity as an important factor influencing stability of organic solar cells

In the pursuit of advancing the commercialization of organic solar cells (OSCs), stability emerges as a paramount challenge. Herein, we show that the electron transport connectivity is a key factor determining the electron transport and device stability of OSCs. When compared to small molecular acceptors (SMAs), the larger-size polymeric acceptors (PAs) are likely to establish an electron transport network with superior connectivity. This enhanced connectivity enables more robust electron transport during potential device degradation. Our findings indicate that PA-integrated devices sustain elevated electron mobilities, even under reduced acceptor ratios (or higher impurity doping) over prolonged device operation. Furthermore, we employ the refined Su-Schrieffer-Heeger tight-binding model, in tandem with a random electron passing test and algebraic connectivity evaluations of molecular configurations, to conclusively validate the pivotal role played by the electron transport connectivity. These revelations are poised to offer new perspectives for material choices and methodologies for improving stability of OSCs.