Enhanced Intramolecular Hole Transfer in Block Copolymer Enables >15% and Operational Stable Single‐Material–Organic Solar Cells

• Published in: Advanced materials (Weinheim) 2024-11, Vol.36 (46), p.e2408988-n/a
• Main Authors: Li, Bin, Kong, Yuxin, Li, Tao, Li, Hongxiang, Zhao, Haibin, Cheng, Pei, Yuan, Jianyu
• Format: Article
• Language: English
• Subjects: Absorption spectroscopy; block copolymer; Block copolymers; Bulk polymerization; carrier dynamic; Charge transfer; Efficiency; Energy conversion efficiency; Excitation spectra; Excitons; Heterojunctions; Molecular structure; morphology; Optical properties; organic solar cells; Photovoltaic cells; Solar cells; stability; Synthesis; Transport properties
• ISSN: 0935-9648; 1521-4095; 1521-4095
• DOI: 10.1002/adma.202408988

Recent studies on narrow bandgap all‐conjugated block copolymer (BCP) single‐material–organic solar cells (SMOSCs) have made unprecedented progress in power conversion efficiency (PCE); however, it still lacks understanding of the structure‐property relationship in these highly mixed materials. Herein, the impact of different synthetic protocols (direct synthesis (d‐BCP) versus sequential synthesis (s‐BCP)) is first investigated on the relevant photovoltaic properties. Targeting the same BCP, namely PBDB‐T‐b‐PYIT, it is found that the change in polymerization reaction leads to quite different optical and transport properties. The d‐BCP outputs a record‐high PCE of 15.02% for SMOSCs as well as enhanced operation stability under simulated 1‐sun illumination, which is significantly higher than that of s‐BCP (10.33%) and even close to its bulk heterojunction (BHJ) counterparts. Detailed transient absorption spectroscopy reveals ultrafast dynamics of charge transfer (CT) and exciton dissociation in BCP. In together with morphology characterization, it is revealed that the d‐BCP has more phase pure composition, enhanced molecular ordering, and higher intramolecular CT efficiency relative to those of s‐BCP. These findings gain insight into both the structure and carrier dynamic of BCP and demonstrate the possibility of achieving high‐efficiency and stable SMOSCs. The impact of different synthetic protocols of block copolymer (BCP) is first investigated on the relevant photovoltaic properties. The more phase pure direct synthesis BCP exhibits enhanced intramolecular hole transfer, leading to a record efficiency of over 15% for single‐material–organic solar cells together with excellent long‐term operational stability.