研究目的
To investigate the effect of the metal work function on the surface passivation of aluminum-oxide-passivated n-type crystalline silicon wafers and to suggest a suitable metal work function range to optimize contact recombination in silicon-based solar cells.
研究成果
The impact of metal work function on the surface passivation at a passivating contact was investigated using the QSSPL technique. A significant change in J0m was observed when applying a metal layer onto the 5-nm-thick AlOx passivation layer, attributed to the change in minority-carrier concentration near the c-Si surface. This effect is suppressed when the AlOx layer thickness is increased. Suitable metals should exhibit work function values below that of n-type or above that of p-type c-Si to benefit from the asymmetric carrier population induced by the metal in passivating-contact-based solar cells.
研究不足
The study is limited to n-type crystalline silicon wafers and aluminum oxide passivation layers. The impact of metal work function on J0m is more pronounced for thinner passivation layers, and the effect is suppressed when the AlOx layer thickness is increased. More measurements are required within the range of metal work functions higher than that of n-type c-Si to clarify the trend of J0m.
1：Experimental Design and Method Selection:
The study uses the quasi-steady-state photoluminescence (QSSPL) technique to measure the injection-dependent minority-carrier lifetime and to extract the surface recombination current density (J0s) using the Kane-Swanson method.
2：Sample Selection and Data Sources:
Commercial n-type Czochralski-grown silicon wafers with a thickness of 180±10 μm and a resistivity of 6 ??cm are used.
3：List of Experimental Equipment and Materials:
Aluminum oxide (AlOx) films with a thickness of 5 or 20 nm were deposited by atomic layer deposition as passivation layers. Five different metal layers are used: lithium-fluoride/aluminum (LiF/Al), magnesium (Mg), Al, silver (Ag), palladium (Pd), molybdenum-oxide/Ag (MoOx/Ag).
4：Experimental Procedures and Operational Workflow:
The wafers were RCA cleaned and then dipped in hydrofluoric acid solution to remove the native oxide prior to subsequent processing steps. Metal contact layers were thermally evaporated at the rear side of the structures.
5：Data Analysis Methods:
The Auger-corrected inverse lifetime is used to assess the surface recombination, and the data is fitted at excess carrier concentrations (Δn) at least ten times larger than the wafer doping (Ndop) using the Kane-Swanson method.
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