High-Efficiency and Mechanically Robust All-Polymer Organic Photovoltaic Cells Enabled by Optimized Fibril Network Morphology

All-polymer organic photovoltaic (OPV) cells possessing high photovoltaic performance and mechanical robustness are promising candidates for flexible wearable devices. However, developing photoactive materials with good mechanical properties and photovoltaic performance so far remains challenging. In this work, a polymer donor PBDB-TF with a high weight-average molecular weight (M-w) is introduced to enable highly efficient all-polymer OPV cells featuring excellent mechanical reliability. By incorporating the high-M-w PBDB-TF as a third component into the PBQx-TF:PY-IT blend, the bulk heterojunction morphology is finely tuned with a more compact pi-pi stacking distance, affording efficient pathways for charge transport as well as mechanical stress dissipation. Hence, all-polymer OPV cells based on the ternary blend film demonstrate a maximum power conversion efficiency (PCE) of 18.2% with an outstanding fill factor of 0.796. The flexible OPV cell delivers a decent PCE of 16.5% with high mechanical stability. These results present a promising strategy to address the mechanical properties and boost the photovoltaic performance of all-polymer OPV cells.

Automated summary

The researchers have successfully achieved high efficiency and mechanical reliability in all-polymer organic photovoltaic (OPV) cells by introducing a polymer donor, PBDB-TF, with a high molecular weight. By adding the high molecular weight PBDB-TF as a third component into the PBQx-TF:PY-IT blend, they optimized the heterojunction morphology, enhancing charge transport efficiency and mechanical stress dissipation. As a result, the all-polymer OPV cells based on the ternary blend film showed a maximum power conversion efficiency (PCE) of 18.2% with a fill factor of 0.796. The flexible OPV cell also achieved a decent PCE of 16.5% with high mechanical stability. These findings provide a promising strategy for improving the mechanical properties and boosting the photovoltaic performance of all-polymer OPV cells.