Efficiency Improvement of NiO_<i>x</i>‐Based Hole Transport Layers in Passivated Contact Crystalline Silicon Solar Cells

Passivated contact crystalline silicon ( c ‐Si) solar cells with nickel oxide (NiO x ) as a hole transport layer (HTL) are a promising and efficient solar cell that has received much attention. However, the current low open circuit voltage ( V oc ) and low stability of c ‐Si solar cells with NiO x as the HTL are due to the bad passivation and the ion diffusion, which has limited the development of NiO x ‐based c ‐Si solar cells. Herein, the performance of doping‐free asymmetric passivated contact c ‐Si heterojunction solar cells is improved by using hydrogen‐doped aluminum oxide (HAl 2 O 3 ) as the passivation layer and annealing in forming gas (nitrogen, hydrogen mixture FGA), as well as by introducing an economically saving composite Ni/Ag electrode. Finally, a 20.29% power conversion efficiency is achieved from p ‐Si/HAl 2 O 3 (FGA)/NiO x /Ni/Ag back‐contact c ‐Si solar cells, which is the highest efficiency reported so far for c ‐Si solar cells with NiO x as the HTLs. Furthermore, the efficiency of the p ‐Si/HAl 2 O 3 (FGA)/NiO x /Ni/Ag remains above 20% after 30 days of storage in an atmospheric environment, demonstrating its long‐term stability. This study demonstrates the potential for industrialization of NiO x ‐based HTL c ‐Si solar cells with high performance and high stability.