Low Oxygen Content MoO_x and SiO_x Tunnel Layer Based Heterocontacts for Efficient and Stable Crystalline Silicon Solar Cells Approaching 22% Efficiency

In crystalline silicon (c-Si) solar cells, the hole transport layer (HTL) made of high oxygen content MoOx (x > 2.85, H-MoOx) evaporating from molybdenum trioxide is not ideal due to low optical bandgap and interface reaction effects. This limits the power conversion efficiency (PCE) and stability of c-Si solar cells. To improve this, low oxygen content MoOx (x < 2.85, L-MoOx) with a wide bandgap of 3.87 eV, deposited using molybdenum dioxide (MoO2), is explored and implemented. The c-Si/SiOx (FGA, forming gas annealing)/L-MoOx heterojunction has a low contact resistivity of approximate to 15.06 m Omega cm(2), which is almost one order of magnitude lower than that of c-Si/SiOx(FGA)/H-MoOx heterojunction. Using L-MoOx as the HTL, a c-Si solar cell based on the SiOx passivation layer shows a fill factor of 84.38% and PCE of 21.75%, representing the highest efficiency for MoOx-based p-type c-Si solar cells. Scanning transmission electron microscopy results show that the L-MoOx HTL effectively enhances the stability of c-Si solar cells when exposed to air by reducing Ag and Si element diffusion into MoOx. This successful preparation of efficient and stable MoOx HTL films, while preserving their field-effect passivation ability, provides valuable insights into the development of high-performance HTL.