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

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.