Low Oxygen Content MoO<sub>x</sub> and SiO<sub>x</sub> Tunnel Layer Based Heterocontacts for Efficient and Stable Crystalline Silicon Solar Cells Approaching 22% Efficiency
Jingjie Li, Kang Qian, Yanhao Wang, Zixiao Zhou, Zhaoqing Sun, Hai Zhang, Wanyu Lu, Xianglin Tao, Shan‐Ting Zhang, Xiaoqing Chen, Zilong Zheng, Hui Yan, Dongdong Li, Yongzhe Zhang
Abstract
Abstract In crystalline silicon ( c‐ Si) solar cells, the hole transport layer (HTL) made of high oxygen content MoO x ( x > 2.85, H‐MoO x ) 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 MoO x ( x < 2.85, L‐MoO x ) with a wide bandgap of 3.87 eV, deposited using molybdenum dioxide (MoO 2 ), is explored and implemented. The c ‐Si/SiO x (FGA, forming gas annealing)/L‐MoO x heterojunction has a low contact resistivity of ≈15.06 mΩ cm 2 , which is almost one order of magnitude lower than that of c‐Si/SiO x (FGA)/H‐MoO x heterojunction. Using L‐MoO x as the HTL, a c ‐Si solar cell based on the SiO x passivation layer shows a fill factor of 84.38% and PCE of 21.75%, representing the highest efficiency for MoO x ‐based p ‐type c ‐Si solar cells. Scanning transmission electron microscopy results show that the L‐MoO x HTL effectively enhances the stability of c ‐Si solar cells when exposed to air by reducing Ag and Si element diffusion into MoO x . This successful preparation of efficient and stable MoO x HTL films, while preserving their field‐effect passivation ability, provides valuable insights into the development of high‐performance HTL.