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Low Work Function Ytterbium Silicide Contact for Doping-Free Silicon Solar Cells
摘要： Metal silicide is a well-known material for contact layers, however, it has not been tested in the context of doping-free carrier selective contacts. Thin film deposition of an appropriate metal with mild annealing treatment is an interesting alternative to the more complex depositions of other compound materials. Reaction of Yb deposited on top an i-a-Si:H passivation layer results in the formation of YbSix on top of a remnant i-a-Si:H following a low-temperature anneal below 200 °C. Such a contact is an interesting candidate as a doping-free electron-selective contact. Detailed investigation of the i-a-Si/YbSix contact shows that Yb thickness, i-a-Si:H thickness and silicidation annealing conditions play a significant role in determining the recombination current density (J0,metal) and the contact resistivity (ρc). Low J0,metal of 5 fA/cm2 and low ρc below 0.1 ?.cm were independently demonstrated for such i-a-Si:H/YbSix contacts. We also demonstrate that low-temperature silicidation can be combined with contact sintering (160 °C/25 min) or module lamination (160 °C/20 min), which are potential pathways for process simplification. Combining the optimised i-a-Si:H/YbSix electron contact with MoOx based hole contact in the MolYSili doping-free cell (i-a-Si:H/MoOx+ i-a-Si:H/YbSix), we achieved 16.7 % in average efficiency and 17.0 % for the champion cell. Furthermore, the YbSix contact stability was evaluated at module level and excellent thermal stability of the MolYSili laminate was demonstrated using the damp-heat test method (humidity 85 %, 85 °C, 1000 h), where the laminated MolYSili cell did not show any degradation in the cell efficiency. This is the first proof-of-concept demonstration of a stable silicide-based contact for low-temperature processed doping-free solar cells.
关键词： Yb silicide,electron-selective contact,passivating contact,doping-free cells,pinning
更新于2025-09-23 15:19:57
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Contributions to the Contact Resistivity in Fired Tunnel-Oxide Passivating Contacts for Crystalline Silicon Solar Cells
摘要： In this article, we investigate the contact resistivity of p-type passivating contacts for silicon solar cells. Our contact structures are compatible with firing, a rapid annealing process similar to the one used for sintering of the screen-printed metallization in solar cell manufacturing. We find that the short firing process crystallizes the doped layers and incorporates active boron dopants up to the solubility concentration at the chosen firing temperature. The dependence of our contact resistivities on carrier density and temperature suggest that the hole transport is a combination of tunneling through the oxide at the wafer surface and of thermionic field emission over the Schottky barrier to the metallization. For ideal firing conditions, we find implied open-circuit voltages up to 720 mV and contact resistivities as low as 15 m·Ω·cm2.
关键词： silicon solar cell,passivating contact,Contact resistivity
更新于2025-09-16 10:30:52
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Optimization of Transparent Passivating Contact for Crystalline Silicon Solar Cells
摘要： A highly transparent front contact layer system for crystalline silicon (c-Si) solar cells is investigated and optimized. This contact system consists of a wet-chemically grown silicon tunnel oxide, a hydrogenated microcrystalline silicon carbide [SiO2/μc-SiC:H(n)] prepared by hot-wire chemical vapor deposition (HWCVD), and a sputter-deposited indium doped tin oxide. Because of the exclusive use of very high bandgap materials, this system is more transparent for the solar light than state of the art amorphous (a-Si:H) or polycrystalline silicon contacts. By investigating the electrical conductivity of the μc-SiC:H(n) and the influence of the hot-wire filament temperature on the contact properties, we find that the electrical conductivity of μc-SiC:H(n) can be increased by 12 orders of magnitude to a maximum of 0.9 S/cm due to an increased doping density and crystallite size. This optimization of the electrical conductivity leads to a strong decrease in contact resistivity. Applying this SiO2/μc-SiC:H(n) transparent passivating front side contact to crystalline solar cells with an a-Si:H/c-Si heterojunction back contact we achieve a maximum power conversion efficiency of 21.6% and a short-circuit current density of 39.6 mA/cm2. All devices show superior quantum efficiency in the short wavelength region compared to the reference cells with a-Si:H/c-Si heterojunction front contacts. Furthermore, these transparent passivating contacts operate without any post processing treatments, e.g., forming gas annealing or high-temperature recrystallization.
关键词： solar cell,tunneling,silicon,silicon carbide,transparent passivating contact (TPC),selective contact,photovoltaic cells,Passivating contact
更新于2025-09-11 14:15:04
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Thermal stability improvement of metal oxide-based contacts for silicon heterojunction solar cells
摘要： Metal oxides are interesting materials for use as carrier-selective contacts for the fabrication of doping-free silicon solar cells. In particular, MoOx and TiOx have been successfully used as hole and electron selective contacts in silicon solar cells, respectively. However, it is of paramount importance that good thermal stability is achieved in such contacts. In our work, we combined i-a-Si:H/MoOx based hole contacts with electron contacts featuring i-a-Si:H/TiOx/low work function metal (ATOM) to fabricate doping-free cells, termed MolyATOM cells. We found that the thermal stability of the ATOM contact was improved when the i-a-Si:H was annealed (300°C for 20 min in N2) before depositing TiOx (i.e. pre-TiOx annealing), which reduces the hydrogen content in i-a-Si:H by about 27 %rel, and thereby the H-related degradation of the ATOM contact characteristics. Moreover, it was found that reducing the thickness of the low-work function metal on top of the TiOx enhanced the thermal stability of the ATOM contact. With these adaptations, the MolyATOM cell efficiency was improved by 3.5 %abs, with the highest efficiency of 17.6%. Moreover, the cells show improved thermal stability after the above-mentioned pre-TiOx annealing, which is confirmed by annealing tests at cell level as well as damp-heat tests at module level. The insights of this study could be used to tailor other metal-oxide based electron or hole contacts.
关键词： Doping-free cells,Passivating contact,MoOx,Thermal stability,TiOx,Annealing
更新于2025-09-11 14:15:04