Design and simulation of PEA0.15FA0.75MA0.1SnI2Br based quasi-2D/3D tin perovskite solar cells with different charge transport layers for efficiency enhancement

Wide-bandgap (WBG) tin-based perovskite solar cells (PSCs) have emerged as promising lead-free alternatives to conventional lead halide devices due to their improved environmental compatibility. However, their performance is often limited by high trap-state density, moisture-induced oxidation of Sn ²⁺ , and rapid crystallization. Compositional engineering enables the formation of a quasi-2D/3D perovskite structure through the incorporation of hydrophobic phenylethylammonium (PEA⁺) cations into WBG tin-based perovskite. This structural modification promotes preferential orientation and enhanced crystallinity of the 3D phase, while the 2D component passivates grain boundaries, suppresses moisture penetration, and mitigates Sn ²⁺ oxidation. In addition, PEA⁺ incorporation modulates the band structure, facilitating improved charge transfer at the transport layer interfaces. In this work, SCAPS-1D is employed to numerically investigate quasi-2D/3D PEA _0.15 FA _0.75 MA _0.1 SnI ₂ Br-based PSCs, with emphasis on interface optimization and transport layer selection. Electric field distribution and energy band alignment at the interfaces are systematically analyzed due to their critical role in carrier extraction and device efficiency. Furthermore, the effects of absorber thickness, defect density, operating temperature, and back metal work function are examined to identify optimal device configurations. The observations revealed that C ₆₀ and Cu ₂ O exhibit more suitable band alignment and better charge extraction properties. After comprehensive optimization, the device achieves an open-circuit voltage of 0.93 V, a short-circuit current density of 18.46 mA cm⁻², a fill factor of 81.21%, and a maximum power conversion efficiency of 14.2%. The simulation results provide valuable insights into the interplay between absorber composition, interface energetics, and electric field profiles, guiding the development of stable, high-efficiency, lead-free WBG tin-based PSCs.