Effective Hydrogenation Strategies to Boost Efficiency over 20% for Crystalline Silicon Solar Cell with Al₂O₃/Cu₂O Passivating Contact

Abstract

Passivation interlayers such as Al 2 O 3 are required to improve the hole selectivity of dopant-free passivating contact based on transition metal oxides. For the interlayer to provide low surface recombination as in conventional silicon heterojunctions (SHJs) or tunnel oxide passivated contact (TOPCon) technologies, "hydrogenation" strategies to effectively introduce hydrogen in passivation interlayers while being compatible with transition metal oxides (TMOs) are urgently sought after. In this work, an easy-to-implement strategy to successfully incorporate extra hydrogen in the Al 2 O 3 passivation layer is developed. The chemical and field-effect passivation mechanisms of the extra hydrogen are revealed via comprehensive experimental analyses and density functional theory calculations. By implementing H-Al 2 O 3 with Cu 2 O as the hole-selective rear contact in p-type crystalline silicon (c-Si) solar cells, a remarkable efficiency of 20.35% is achieved (fill factor of 84.76%). The study highlights a promising approach to improve the passivation quality of dielectric interlayers and boost the performance of dopant-free c-Si solar cells to compete against mainstream c-Si photovoltaics technologies.

Dopant‐free passivating contacts for crystalline silicon solar cells: Progress and prospects

“…55 After that, Li et al successfully incorporated additional hydrogen in Al 2 O 3 (denoted as H-Al 2 O 3 ) by replacing pure N 2 with N 2 /H 2 (5 vol.% H 2 ) mixture as the carrier gas during the ALD deposition process. 198 Extensive experimental and simulation results confirm that the additional hydrogen ameliorates both chemical and field-effect passivation by saturating the dangling bonds at c-Si surface and increasing fixed negative charge density, respectively. Implementing H-Al 2 O 3 as the passivation layer boosted the efficiency to 20.35%, which is so far the highest reported for Cu 2 O-based dopant-free passivating contact c-Si solar cells.…”

“…Furthermore, the presence of Al 2 O 3 physically separates Cu 2 O and c ‐Si thereby greatly suppressing interfacial redox reaction and Cu diffusion and finally a high efficiency of 19.7% could be obtained 55 . After that, Li et al successfully incorporated additional hydrogen in Al 2 O 3 (denoted as H‐Al 2 O 3 ) by replacing pure N 2 with N 2 /H 2 (5 vol.% H 2 ) mixture as the carrier gas during the ALD deposition process 198 . Extensive experimental and simulation results confirm that the additional hydrogen ameliorates both chemical and field‐effect passivation by saturating the dangling bonds at c ‐Si surface and increasing fixed negative charge density, respectively.…”

Solution-processed copper(i) iodide via co-doping for enhanced hole selective contacts in p-type crystalline silicon solar cells

“…22 Li et al applied electron-beam evaporated Cu 2 O with the hydrogenated Al 2 O 3 interface passivation layer to obtain a high PCE of 20.35% for Cu 2 O/p-Si heterojunction solar cells. 23 In contrast to copper-based oxides, copper( i ) iodide (CuI) is an excellent hole transport layer with a larger bandgap. 24–26 The relatively lower electronegativity of iodine compared with that of oxygen allows the generation of more delocalized holes above the valence band maximum (VBM), 27 and moreover, its larger radius and the spatially spread three outermost p-orbitals enable sufficient orbital overlap for fast hole transport.…”

Sub‐Stochiometric Nickel Oxide Hole‐Selective Contacts in Solar Cells: Comparison of Simulations and Experiments with Sputtered Films

“…[23] Highest efficiency of 20.35% is achieved by Lee et al with Cu 2 O as the hole-selective rear contact in p-type crystalline silicon (c-Si) solar cells. [24] So far, the highest efficiency of 17.3% was reported by Nayak et al with thermally evaporated substoichiometric nickel oxide (NiO x ) in n-type silicon heterojunction solar cell. [25] Nevertheless, all these data obtained with p-type oxides must be set into comparison with n-type oxides having high work functions.…”