Wide Bandgap Perylene Diimide Derivatives as an Effective Third Component for Parallel Connected Ternary Blend Polymer Solar Cells

Constructing a ternary blend active layer for polymer solar cells (PSCs) is a widely explored approach to achieve a high power conversion efficiency (PCE). To achieve this, multiple approaches have been explored for dual-acceptor PSCs including acceptor alloy and acceptor cascade. Parallel connection is another working mechanism of ternary blends with the advantage of large freedom in the selection of materials with largely different absorption ranges. Here, we purposely designed two propeller-like perylene diimide (PDI) derivatives, TT-PDI and TZ-PDI, with different central cores and selected one as the third component to be added into a PM6:Y6 blend. The highest PCE of 17.52% was obtained with 10% of Y6 replaced by TZ-PDI in the ternary blend. To our knowledge, this is the first report of a PDI derivative to be added into a PM6:Y6 blend with significantly increased device performance. The improved PCE was ascribed to the high photon absorption due to the wide bandgap and amorphous structure of TZ-PDI, which paved a functional parallel charge generation route without interfering with the nanostructure of the PM6:Y6 blend. This work demonstrated the parallel connected ternary blend as a viable route to construct efficient PSCs and a chemical designing strategy for a suitable third component in ternary blends.