A Reliable Strategy to Unravel the Structure and Composition of Semiconducting Conjugated Donor‐Acceptor Block Copolymers

Single-component (SC) polymers are a promising new generation of materials for organic photovoltaics. They offer the potential to combine high power conversion efficiencies with significantly improved stability compared to traditional heterojunction systems that incorporate non-fullerene acceptors (NFAs). Despite this potential, the structural characterization of SC polymers is limited in the literature and is often insufficiently detailed. In this study, we present a rigorous and comprehensive strategy for elucidating the structure of these materials, which enables a deeper understanding of their architecture and structure-property relationships. We describe a characterization protocol for a model SC polymer based on the donor polymer PTQ10 and an NFA-based polymer PIDTe. Using a model small molecule approach, we identify the characteristic heterojunctions' proton NMR signals and confirm their formation within the materials with the help of various 2D NMR methods. For the first time, we quantify the average number of heterojunctions (NoH) in the copolymers. We synthesize two additional SC polymers and demonstrate that our method can be applied to these systems, with the potential to be applied to others. This study establishes a reliable strategy for the accurate characterization of SC polymers intended for use in organic electronics and organic photovoltaics applications. A. C carried out the synthesis and performed the characterizations and analyzed the raw data. P-A. B developed the NMR pulse sequences and optimized the NMR protocols. L. R and Y. K contributed to the synthesis. C. A acquired the funding and supervised the study. A. C wrote the manuscript, R. D and C. A corrected and edited the manuscript and all the authors reviewed the manuscript and have given their approval to the final version.