Novel Interlayer Boosting the Performance of Evaporated Cu₂O Hole‐Selective Contacts in Si Solar Cells

Abstract

Passivating contacts based on transition metal oxides are of great interest for applications in crystalline silicon (c‐Si) solar cells due to their improved optical transparency and potential cost reduction. In this work, the contact resistivity and passivation for thermally evaporated Cu2O are investigated and optimized, with and without an Al2O3 interlayer, as a hole‐selective contact to c‐Si. Additionally, we implement an Al y TiO x /TiO2 stack as a novel passivating tunnel interlayer for hole‐selective contacts, achieving an implied open‐circuit voltage iV oc of 630 mV and a record‐low J 0 of 212 fA cm−2 while maintaining a contact resistivity ρ c of 62 mΩ cm2. A record‐low ρ c of 8 mΩ cm2 for Cu2O‐based contacts is also demonstrated at the expense of passivation. The addition of the interlayer resulted in a 2% absolute improvement in the efficiency of proof‐of‐concept c‐Si cells with full‐area rear Cu2O contacts, reaching 19.1%.The demonstration of this novel interlayer stack provides new avenues to improve the performance also of other hole‐selective passivating contacts.

Investigation of H2 Plasma Incorporated ALD-TiOx Films as Hole-Selective Passivating Contacts in Crystalline Silicon Solar Cells

“…This new film stack also exhibited better thermal stability, with ρ c decreasing as the deposition temperature increased, attributed to ZnO's lower bulk resistivity and higher carrier mobility and concentration. 43 Additionally, Bartholazzi et al 44 applied the Al y TiO x /TiO 2 stack as an interlayer to enhance hole selectivity in Cu 2 O. They found that by reducing the thickness of the stack to allow the transport of holes through tunneling, the work function of Cu 2 O increased from 4.63 to 4.74 eV.…”

“…This new film stack also exhibited better thermal stability, with ρ c decreasing as the deposition temperature increased, attributed to ZnO's lower bulk resistivity and higher carrier mobility and concentration. 43 Additionally, Bartholazzi et al 44 To date, the highest efficiency achieved by c-Si solar cells using a TiO x -based electron-selective contact is 23.1%. This was accomplished with a partial rear contact configuration, where the rear side was predominantly passivated by SiN x , with small openings that allow a TiO x /LiF x /Al stack to contact the n-Si.…”