Voltage loss mitigation in triple-cation perovskite solar cells through 2D-BA2PbI4 interface passivation: A numerical investigation towards tandem architectures

Interfacial defect-mediated recombination is a key limitation to achieving high open-circuit voltage (V OC ) in three-dimensional triple-cation perovskite (3D-TCP) solar cells. Herein, a comprehensive device passivation strategy is employed on Cs 0.03 FA 0.945 MA 0.025 Pb(I 0.975 Br 0.025 ) 3 using the physics-based SCAPS-1D simulator to investigate the influence of device optimisation, interface passivation, and tandem integration. We first examined a control device using absorber-thickness engineering, followed by a systematic sensitivity analysis that included bulk defect density, series and shunt resistances, together with temperature-dependent stability analysis. The optimised control device achieved a V OC of 1078.7 mV, with a significant total voltage loss of 491.3 mV. This confirmed that interfacial recombination is the main performance-limiting factor. To address this issue, we subsequently introduced a two-dimensional BA 2 PbI 4 Ruddlesden-Popper perovskite layer at the 3D-TCP/HTL interface. This addition helped to passivate interfacial defects and suppress nonradiative recombination, leading to a remarkable increase in V OC to 1134.0 mV. Additionally, the total voltage loss decreases significantly to 436.0 mV. Further, these optimised standalone control and passivated devices have been employed to simulate two-terminal (2T) monolithic and four-terminal (4T) mechanically stacked tandem configurations. The best simulated 2T monolithic and 4T mechanically stacked tandem solar cells yielded the PCE of 31.27% and 31.47%, respectively. This work highlights that interface passivation, supported by sensitivity and thermal stability analyses, is an effective strategy for minimising recombination losses. These improvements will contribute to the advancement of high-efficiency triple-cation perovskite and tandem photovoltaic technologies.