Carboxylate substituted pyrazine: A simple and low-cost building block for novel wide bandgap polymer donor enables 15.3% efficiency in organic solar cells

In addition to high power conversion efficiency (PCE) and good stability, the low-cost of photovoltaic materials is also very important for the practical application of organic solar cells (OSCs). Herein, we synthesized a carboxylate substituted pyrazine-based electron-deficient building block (DTCPz) with a simple structure and low synthetic cost, and then developed a novel wide bandgap polymer donor PFBCPZ. Due to the synergistic electron-withdrawing effects of the fluorination in donor unit (BDT-TF) and esterification and C=N double-bond in DTCPz unit, PFBCPZ shows a deeper HOMO level of -5.60 eV, a strong intermolecular ?-? interaction, good crystallinity and stacking, and high hole-mobility of 2.11 ? 10-3 cm2 V-1 s- 1. Matched with a low bandgap acceptor IT-4F, excellent charge transfer, weak recombination, and small non-radiative energy loss in OSCs was achieved, resulting in an impressive fill factor of 0.785 and a high open-circuit voltage of 0.92 V. As a result, a PCE of up to 15.3% is obtained in OSCs, which is the highest value in the IT-4F-based binary OSCs so far and indicates that low-cost DTCPz with a simple structure is a promising building block to construct highperformance polymer donors for application in efficient OSCs.

Automated summary

A novel wide bandgap polymer donor PFBCPZ was developed in this study, which achieved a high power conversion efficiency in organic solar cells (OSCs) when matched with a low bandgap acceptor IT-4F. This demonstrates the potential of low-cost, simple structured DTCPz as a promising building block for high-performance polymer donors in efficient OSCs.