An asymmetric polymerized small molecular acceptor with temperature-dependent aggregation and superior batch-to-batch reproducibility for efficient all-polymer solar cells

Abstract

Polymerized small molecular acceptors (PSMAs) have been instrumental in driving the advancements in power conversion efficiencies (PCEs) of all -polymer solar cells (all-PSCs). However, PSMAs commonly face challenges such as low molecular weights and notable batch -to -batch variation, posing significant obstacles to the transition of all-PSCs from lab to fab. Herein, a novel PSMA, which we refer to PAY -IT with an asymmetric conjugated skeleton is reported. The A-D1A'D2-A-type asymmetric monomer endows PAY -IT a random conjugated backbone, thus offering a desired temperature dependent aggregation behavior, which is hardly observed in conventional PSMAs. This characteristic facilitates chain growth during polymerization, thus yielding high molecular weights and low batch -to -batch sensitivity for the polymer. Moreover, the "S -shape" configuration of the asymmetric monomer endows PAY -IT good planarity and excellent charge transport property. As a result, the all-PSC consisted of PAY -IT and PM6 showcased a remarkable PCE of 14.9 %. More importantly, three batches of PAY -IT with number -average molecular weights ranging from 18.3 to 26.2 kDa exhibited nearly identical PCE (14.4-14.9 %), demonstrating superior batch -to -batch reproducibility of this polymer acceptor. This work explored PSMAs with asymmetric skeleton for the first time, and the results demonstrated a new design concept for the development of state-of-the-art PSMAs with minimal batch -to -batch variation.