Researchers have developed a perovskite-silicon tandem solar cell with an inverted perovskite top cell using a new polymer hole-transport layer (HTL) to promote uniform perovskite deposition and create a homogeneous hole-selective interface. The new copolymer, PNCC, combines the charge-transport properties of PTAA-like polymers with the strong substrate-binding characteristics of PACz materials, addressing inherent limitations of current organic HTMs. PNCC showed improved film quality, defect passivation, and longer carrier lifetimes, leading to a power conversion efficiency of 26.6% in single-junction perovskite solar cells fabricated under ambient conditions. This development could facilitate the scaling of perovskite solar cell technology for large-area devices produced under ambient conditions. Additionally, a new polymer-based solar cell achieved an efficiency of 26.5%, outperforming other reference cells, and showed high stability, retaining over 90% of its initial efficiency after exposure to high temperatures. When used in tandem cells with silicon, the polymer resulted in a champion device with an efficiency of 33.3%. The researchers believe this technology could lead to scalable and stable high-performance solar cells, presenting a promising pathway for photovoltaic manufacturing.