High-Efficiency Silicon Solar Cells with Chemical and Field-Effect Passivation Using Novel 2PACz/MoOx Hole-Selective Contacts

Dopant-free crystalline silicon (c-Si) solar cells face critical challenges in hole transport layer (HTL) design, where conventional molybdenum oxide (MoO_x) contacts suffer from interface oxidation and insufficient electron blocking. While self-assembled monolayers (SAMs) demonstrate potential in organic photovoltaics, their application in silicon-based HTLs remains unexplored. In this study, a novel organic SAM (2PACz) is proposed, where phosphonic acid (PA) groups form strong coordination bonds with MoO_x as HTL, aiming to improve cell performance via both chemical and field-effect passivation. The incorporation of 2PACz raises the work function of MoO_x by 0.66 eV and significantly improves the minority carrier lifetime, which, in turn increases the built-in potential (V_bi) to 1.06 V. These improvements contribute to a boost in both open-circuit voltage (V_oc) and short-circuit current (J_sc). Finally, the solar cell with 2PACz/MoO_x-Au NPs-MoO_x (MAM) stack achieves a V_oc of 753.3 mV, a J_sc of 40.10 mA cm⁻², a fill factor (FF) of 79.12%, and a conversion efficiency (E_ff) of 23.90%. The application of 2PACz in the HTL significantly enhances solar cell performance, offering a novel strategy for interface optimization in c-Si solar cells and other optoelectronic devices.