Comparative Study of Buffer Layers in Carbon Nanotube Based Heterostructure Solar Cells: A Numerical Simulation Approach

ABSTRACT Heterostructure solar cells attract significant interest due to the demand for high‐efficiency and low‐cost photovoltaic technologies. The buffer layer plays a crucial role in determining band alignment, reducing interfacial defects, and improving charge transport, stability, and device performance. This study investigates a ZnO/Buffer Layer/SWCNT/Cu 2 O solar cell structure using SCAPS‐1D, where Single‐Walled Carbon Nanotubes serve as the absorber and Cu 2 O as the back surface field. Three buffer materials PCBM, WO 3 and C 60 are analyzed, and the SWCNT absorber thickness, acceptor concentration, and defect density are varied to determine optimal conditions. The optimal configuration is achieved with PCBM at an absorber, N A = 4 × 10 16 cm −3 and W = 1000 nm at 300 K, producing a power conversion efficiency of 32.90%, J SC = 42.98 mA/cm 2 , V OC = 0.89 V, and FF = 85.87% under AM 1.5G illumination. PCBM shows superior performance compared to WO 3 (32.28%) and C 60 (30.93%) due to favorable energy‐band alignment and lower recombination rate. The findings indicate that buffer‐layer engineering plays a significant role in improving heterostructure solar cell performance and supports the development of efficient, environmentally friendly, and scalable photovoltaic technologies. Furthermore, the materials are non‐toxic and abundant in the Earth's crust, making the structure suitable for photovoltaic applications.