Synergic MXene and S‐benzyl‐L‐cysteine Passivation Strategies for Wide Bandgap Perovskite Solar Cells for 4T Tandem Applications

Abstract Bilayer nickel oxide (NiO_x)/[2‐(3,6‐dimethoxy‐9H‐carbazol‐9yl) ethyl] phosphonic acid (MeO‐2PACz) hole transport layers have become attractive for perovskite solar cells and tandem architectures. However, challenges such as the instability of NiO_x ink, hole accumulation, and trap‐assisted non‐radiative recombination at the interface remain major drawbacks for using NiO_x/MeO‐2PACz HTL bilayer. In this work, two synergic strategies are employed to address these issues such as the doping of the NiO_x ink with niobium (Nb)‐based MXene) and the introduction of S‐benzyl‐L‐cysteine (SBLC) molecule to passivate the MeO‐2PACz/perovskite interface. These modifications effectively reduced defect states in the perovskite layer and enhanced the dipole moment of MeO‐2PACz, minimizing the valence band offset at the MeO‐2PACz/perovskite interface with the reduction of the charge recombination rates. Consequently, the target PSC device, made of 1.68 eV‐bandgap perovskite, demonstrated a power conversion efficiency (PCE) of 19.5% and improved stability compared to the control device when tested under ISOS protocols. Furthermore, semi‐transparent (ST) PSCs have been fabricated for application in 4T tandem perovskite‐silicon cell showing PCE of 18.15% and 27.95% in single‐junction and in tandem architectures, respectively. These findings demonstrate the effectiveness of combining strategic doping and passivation techniques for inverted PSCs enhancing the device performance without discarding long‐term stability.