Advancing High-Performance Organic Solar Cells with Carbazole-Modified 2PACz for Scalable Large-Area Fabrication

The self-assembling molecule 2PACz tends to aggregate in thin films, which negatively impacts the performance of organic solar cells (OSCs) when used as a hole-transporting layer (HTL), particularly in large-area devices. To overcome this, a binary conjugated molecular system incorporating carbazole (Cz), which shares a similar backbone with 2PACz, is introduced. Despite the strong aggregation tendencies of 2PACz and Cz individually, their blend forms homogeneous films due to hydrogen bonding interactions between the two molecules. These interactions suppress 2PACz aggregation, resulting in smooth and well-ordered films. Devices with the modified HTL show significantly enhanced charge transfer, achieving a power conversion efficiency (PCE) of 20.10%, a fill factor of 80.3%, and a short-circuit current of 28.98 mA cm⁻², outperforming those with unmodified 2PACz. Large-area devices (1.0 cm²) with the modified HTL achieve a record-high PCE of 18.56% and a retention rate of 92.7%, compared to 43% for devices with 2PACz. These findings highlight the potential of carbazole-modified 2PACz to improve both efficiency and stability in OSCs, offering a promising strategy for high-performance HTL development.