Co-crystallization of Fibrillar Polymer Donors for Efficient Ternary Organic Solar Cells
Donghui Li, Liang Wang, Chuanhang Guo, Yating Liu, Bojun Zhou, Yiwei Fu, Jing Zhou, Dan Liu, Wei Li, Tao Wang
Abstract
Ternary strategy is identified as an effective method to fine-tune the optoelectronic properties of the photoactive layer of organic solar cells (OSCs) toward high power conversion efficiency (PCE). Although numerous high-performance ternary OSCs have been established, the underlying fundamentals of ternary OSCs are still not fully understood, and a general rule for the ternary system design is highly appreciated. In this contribution, we demonstrate the construction of high-performance ternary OSCs via the co-crystallization of conjugated host donor PM6 and guest donor D18-Cl. Due to the similar chemical structure, larger planarity, and lower surface energy of D18-Cl, it locates in the PM6 phase and organizes with PM6 during solution casting, leading to the formation of co-crystallized fibrillar donor phase with enhanced structural order and charge transport channels. As a result, a series of binary host systems, including PM6:BTP-4F-C6-16, PM6:Y6, and PM6:Y7-BO obtained enhanced efficiency with the presence of D18-Cl as the guest donor, achieving a superior PCE of 18.5% in the PM6:D18-Cl:BTP-4F-C6-16 ternary OSCs. This work is the first demonstration of co-crystallized polymer donor fibrils to boost the charge transport and power conversion of ternary OSCs.