High-Efficiency Digital Inkjet-Printed Non-Fullerene Polymer Blends Using Non-Halogenated Solvents

Inkjet printing (IJP) of polymer solar cells is ideal for small-area off-grid electronics with low power consumption. However, IJP is quite a complex technique compared with techniques such as spin coating or doctor blading. The IJP of polymer blends is reported based on ITIC derivatives as non-fullerene acceptors (NFAs) using non-halogenated solvents. The results show that fluorination of NFA is essential to form highly stable inks in o-xylene, because ITIC has significantly insufficient solubility compared with ITIC-4F. The importance of tetralin as a multifunctional co-solvent for printing highly efficient PM6:ITIC-4F blends is demonstrated, as even at very low concentrations, tetralin not only improves ink jettability and open nozzle time, but also improves drying behavior of the blend layer, resulting in blends with homogeneous micro- and nanoscale morphology. The resulting solar cells using inkjet-printed polymer blends show a maximum efficiency of 10.1%. Moreover, IJP produces significant changes in the nanoscale and microscale morphology. In particular, the formation of a thin PM6 capping layer on the blend surface along with improved phase separation and crystallinity in both the donor and acceptor greatly reduces the recombination of charge carriers in thick blends, making inkjet-printed photoactive films very promising for industrial applications.