Tuning of Aromatic Amine Polymer Side chains for Application as Hole Transport Materials in Wide-Bandgap Perovskite Solar Cells

Perovskite solar cells (PSCs) hold strong potential for efficient and cost-effective photovoltaic technology, yet their device performance and stability remain hindered by interfacial limitations. In particular, the hole transport material (HTM) that contacts both the perovskite and the front contact can often be a bottleneck for device efficiency and durability. To overcome these challenges, we design and synthesize a series of carbazole- and fluorene-based polymers via palladium-catalyzed Buchwald-Hartwig amination, incorporating tunable N,N-dimethyl aminopropyl (N) and butanoate (COOCH₃) side chains. We systematically investigate how these polar side chains affect the electronic properties of the buried perovskite interface and the overall device performance. Our results show that both N and COOCH₃-functionalized HTMs significantly enhance interfacial compatibility with wide-bandgap perovskites, facilitating superior perovskite film formation and more efficient charge extraction. This enhancement yields wide-bandgap PSCs with a champion power conversion efficiency (PCE) of ∼17%, comparable to devices using commercial poly-triarylamine (PTAA) HTMs. These findings highlight that targeted side-chain engineering offers a simple and effective strategy to optimize polymer HTMs for wide-bandgap PSCs, providing valuable insights for the future design of perovskite optoelectronic devices.