Subtle Morphology Control with Binary Additives for High-Efficiency Non-Fullerene Acceptor Organic Solar Cells.

Adding an additive is one of the effective strategies to fine-tune active layer morphology and improve performance of organic solar cells. In this work, a binary additive 1,8-diiodooctane (DIO) and 2,6-dimethoxynaphthalene (DMON) to optimize the morphology of PBDB-T:TTC8-O1-4F-based devices is reported. With the binary additive, a power conversion efficiency (PCE) of 13.22% was achieved, which is higher than those of devices using DIO (12.05%) or DMON (11.19%) individually. Comparison studies demonstrate that DIO can induce the acceptor TTC8-O1-4F to form ordered packing, while DMON can inhibit excessive aggregation of the donor and acceptor. With the synergistic effect of these two additives, the PBDB-T:TTC8-O1-4F blend film with DIO and DMON exhibits a suitable phase separation and crystallite size, leading to a high short-circuit current density (Jsc) of 23.04 mA·cm-2 and a fill factor of 0.703 and thus improved PCE.