Novel Alcohol-Soluble Nitroxide Radical Conjugated Polymer for Cathode Modifier of Efficient Organic Solar Cells with Enhanced Stability

Alcohol-soluble conjugated polymers with polar side-chain components have been regarded as one of the most promising cathode interfacial modifers (CIMs) to achieve high-performance organic solar cells (OSCs). Herein, a novel alcohol-soluble nitrogen oxide radical conjugated polymer (PBN-NO) containing dimethylamine groups for regulating metal work function and the dangling of 2,2,6, 6-tetramethylpiperidine 1-oxy (TEMPO) radical side-chain groups for theoretically improving the conductivity, was prepared and characterized. As compared to the OSCs from PM6:Y6 blends with the most common CIMs of PFN, PDINO, and PDINN, the OSCs with PBN-NO as CIMs provide better or comparable power conversion efficiencies (PCEs) (16.19% vs 13.10%, 15.60%, and 16.15%), enhanced photostability, and thermal stability. Besides that, the reasons for the improving PCEs of the OSCs with PBN-NO modifier are systematically investigated and supported by a set of comparative experiments such as exciton dissociation, charge recombination, capacitance-voltage (C-V), etc. To the best of our knowledge, this is the first report of an alcohol-soluble nitroxide radical conjugated polymer that successfully integrates the interfacial modification of polar groups and improves conductivity by dangling radicals, therefore contributing to efficient OSCs with enhanced stability.

Automated summary

In this study, a novel alcohol-soluble nitrogen oxide radical conjugated polymer (PBN-NO) with dimethylamine groups and TEMPO radical side-chain groups was developed as a cathode interfacial modifer (CIM) in organic solar cells (OSCs). Compared to commonly used CIMs, such as PFN, PDINO, and PDINN, the OSCs with PBN-NO exhibited higher or comparable power conversion efficiencies (PCEs) (16.19% vs 13.10%, 15.60%, and 16.15%), as well as improved photostability and thermal stability. The reasons for the improved PCEs were systematically investigated through various comparative experiments, including exciton dissociation, charge recombination, capacitance-voltage (C-V) measurements, etc. This is the first report on an alcohol-soluble nitroxide radical conjugated polymer that combines the interfacial modification of polar groups and enhanced conductivity through dangling radicals, contributing to efficient OSCs with enhanced stability.