Importance of 2D Conjugated Side Chains of Benzodithiophene-Based Polymers in Controlling Polymer Packing, Interfacial Ordering, and Composition Variations of All-Polymer Solar Cells

Abstract

We delineate the important role of 2D conjugated alkylthiophene side chains of polymers in manipulating the molecular orientation and ordering at the polymer donor/polymer acceptor (PD/PA) interface as well as the composition variations in the blend active layer of all-polymer solar cells (all-PSCs). To systematically investigate the impact of 2D conjugated side chains on the performance of all-PSCs, we synthesized a series of poly(benzo[1,2-b:4,5-b]-dithiophene-thieno[3,4-c]pyrrole-4,6-dione) (PBDTTPD) polymer donors with different contents of alkoxy and alkylthiophene side chains, from 0 to 100% (PBDT-TPD (P1, 100% alkoxy side chain), PBDTT0.29-TPD (P2), PBDTT0.59-TPD (P3), PBDTT0.76-TPD (P4), and PBDTT-TPD (P5, 100% alkylthiophene side chain). The P1–P5 polymer donors produced similar PCEs of ∼6% in fullerene-based PSCs. In contrast, for the all-PSC systems, the changes in the side chain composition of the polymers induced a strong increasing trend in the power conversion efficiencies (PCEs), from 2.8...