Aluminum Halide‐Based Electron‐Selective Passivating Contacts for Crystalline Silicon Solar Cells

Abstract Extensive research has focused on developing wide‐bandgap metal compound‐based passivating contacts as alternatives to conventional doped‐silicon‐layer‐based passivating contacts to mitigate parasitic absorption losses in crystalline silicon (c‐Si) solar cells. Herein, thermally‐evaporated aluminum halides (AlX)‐based electron‐selective passivating contacts for c‐Si solar cells are investigated. A low contact resistivity of 60.5 and 38.4 mΩ cm 2 is obtained on the AlCl x /n‐type c‐Si (n‐Si) and AlF x /n‐Si heterocontacts, respectively, thanks to the low work function of AlX. Power conversion efficiencies (PCEs) of 19.1% and 19.6% are achieved on proof‐of‐concept n‐Si solar cells featuring a full‐area AlCl x /Al and AlF x /Al passivating contact, respectively. By further implementing an ultrathin SiO 2 passivation interlayer and a pre‐annealing treatment, the electron selectivity (especially the surface passivation) of AlX is significantly enhanced. Accordingly, a remarkable PCE of 21% is achieved on n‐Si solar cells featuring a full‐area SiO 2 /AlF x /Al rear contact. AlF x ‐based electron‐selective passivating contacts exhibit good thermal stability up to ≈400 °C and better long‐term environmental stability. This work demonstrates the potential of AlF x ‐based electron‐selective passivating contact for solar cells.