Insulating Polymer Mediated Stability and Photovoltaic Performance of Organic Solar Cells: Influence of Molecular Weight

Insulating polymers are promising components for constructing high performance organic solar cells (OSCs) due to their advantages including low cost, excellent mechanical properties, and feasibility in morphology modulation. However, few studies have been conducted on the effect of molecular weight of insulating polymers on the performance of the corresponding OSCs. In this work, polymethyl methacrylate (PMMA) with different molecular weight (named as PMMAL and PMMAH) are incorporated into a range of polymer:nonfullerene photovoltaic systems. It is found that although both PMMAL and PMMAH can suppress the energetic disorder and the nonradiative energy loss, and lead to enhanced open‐circuit voltage in their corresponding OSCs, distinct mechanical property, operational stability as well as photovoltaic performance are observed. PMMAL can modulate the molecular packing of the host components more effectively due to its superior chain segment mobility during the film‐forming process, which can drive the host components to form more ordered molecular packing and therefore superior photovoltaic performance. On the other hand, due to the better miscibility of PMMAH with the host system, especially the C5‐16 acceptor, PMMAH can be well dispersed in the host and form a stable framework that provides superior mechanical properties and operational stability. Insulating PMMA is demonstrated to mediate the stability and photovoltaic performance of organic solar cells, and exhibits the molecular weight dependence for distinct mechanical property, operational stability, and photovoltaic performance.