Perylene–Diimide Based Non-Fullerene Solar Cells with 4.34% Efficiency through Engineering Surface Donor/Acceptor Compositions

Abstract

Although solvent additive has been observed to positively effect the nanomorphology and, in turn, the electric performance of organic small molecule acceptor based cells, how they act on the donor/acceptor (D/A) compositions throughout the active layer and, consequently, on the electron and hole injection/extraction property is still largely unknown yet. Herein, we use a D/A combination of PBDTTT-C-T (polymer donor) and a perylene diimide (PDI) dimer (small molecule acceptor) and find that the additive of 1,8-diiodooctane (DIO) effectively controls the surface D/A compositions. As pointed out by X-ray photoelectron spectroscopy experiments, the air surface of the active layer is donor-rich and the buried surface is acceptor-rich, while there is a homogeneous distribution of D/A composition across the active layer between the air and the buried surfaces. The donor abundance, i.e., D/A weight ratio, in the acceptor-rich buried surface plays a crucial role in tuning the injection property of selective carrie...