Polymer solar cells:morphology-performance relationship (Pages 104-123)
Recent rapid developments of non-fullerene (NF) small molecular acceptors (SMAs) are the workhorse in the recent amazing surge of the polymer solar cells (PSCs). PSC efficiency increases from 10% to over 16%. The polymer donor-SMA bulk heterojunction (BHJ) film with tunable absorption, sandwiched between two transparent electrodes, assisted by electron-and hole-transport layers, enable semitransparent solar cells to exhibit great potential in versatile applications such as building integrated PV (BIPV). The BHJ morphology is critical and highly dependent on the interplay between the donor and acceptor materials and features thermodynamic and kinetic nature. This paper reviews the progress in morphology understanding of the champion acceptor-donor-acceptor (A-D-A) type SMA based PSCs-from morphology characterization techniques to the design of A-D-A type SMAs, to morphology-performance relationship, and an outlook on the correlation with energy losses for further improving performance of PSCs.