A high recombination rate and high thermal budget for aluminum (Al) back surface field are found in the industrial p-type silicon solar cells. Direct metallization on lightly doped p-type silicon, however, exhibits a large Schottky barrier for the holes on the silicon surface because of Fermi-level pinning effect. As a result, low-temperature-deposited, dopant-free chromium trioxide (CrO , x< 3) with high stability and high performance is first applied in a p-type silicon solar cell as a hole-selective contact at the rear surface. By using 4 nm CrO between the p-type silicon and Ag, we achieve a reduction of the contact resistivity for the contact of Ag directly on p-type silicon. For further improvement, we utilize a CrO (2 nm)/Ag (30 nm)/CrO (2 nm) multilayer film on the contact between Ag and p-type crystalline silicon (c-Si) to achieve a lower contact resistance (40 mΩ·cm). The low-resistivity Ohmic contact is attributed to the high work function of the uniform CrO film and the depinning of the Fermi level of the SiO layer at the silicon interface. Implementing the advanced hole-selective contacts with CrO /Ag/CrO on the p-type silicon solar cell results in a power conversion efficiency of 20.3%, which is 0.1% higher than that of the cell utilizing 4 nm CrO . Compared with the commercialized p-type solar cell, the novel CrO-based hole-selective transport material opens up a new possibility for c-Si solar cells using high-efficiency, low-temperature, and dopant-free deposition techniques.
Dopant-free carrier-selective contacts are becoming increasingly attractive for application in silicon solar cells because of the depositions for their fabrication being simpler and occurring at lower temperatures. However, these contacts are limited by poor thermal and environmental stability. In this contribution, the use of the conductive high work function of cuprous iodide, with its characteristic thermal and ambient stability, has enabled a hole-selective contact for p-type silicon solar cells because of the large conduction band offset and small valence offset at the CuI/p-Si interface. The contact resistivity (≈30 mΩ•cm 2 ) of the Ag/CuI (20 nm)/p-Si contact after annealing to 200 °C represents the CuI-based hole-selective contact with low resistance and high thermal stability. Microscopic images and elemental mapping of the Ag/CuI/p-Si contact interface revealed that a nonuniform, continuous CuI layer separates the Ag electrode and p-type Si. Thermal treatment at 200 °C results in the intermixing of the Ag and CuI layers. As a result, the 200 °C thermal process improves the efficiency (20.7%) and stability of the p-Si solar cells featuring partial CuI hole-selective contact. Furthermore, the devices employing the CuI/Ag contact are thermally stable upon annealing to temperatures up to 350 °C. These results not only demonstrate the use of metal iodide instead of metal oxides as hole-selective contacts for efficient silicon solar cells but also have important implications regarding industrial feasibility and longevity for deployment in the field.
development of dopant-free carrier-selective layer demonstrates
the potential to overcome parasitic absorption and doping-related
recombination caused by heavy doping to realize both low recombination
current density (J
0c) and low contact
resistance (ρc) in simplified procedures. In this
work, thermally evaporated yttrium fluoride (YF3) films
were demonstrated as electron-selective material for c-Si solar cells.
The YF3 interlayers have a low work function of 3.1 eV,
allowing the lowest ρc of 17.8 mΩ·cm2 for the n-Si/YF3/Al contacts.
N-type Si solar cells based on YF3 for electron-passivated
contact were fabricated, reaching an efficiency of 20.8%, an open-circuit
voltage of 645 mV, and a fill factor of 80.8%. This indicates the
future potential application of dopant-free YF3 electron
contact for low-temperature-passivated contact solar cells.
Zinc protective coatings on high carbon SWRH82B-1 steel were sherardized to markedly improve corrosion resistance of the high-strength steel bridge cable wires (SBCW). Sherardizing parameters have been optimized by optical microscopy (OM) /scanning electron microscopy (SEM), X-ray diffraction (XRD) and potentiodynamic polarization tests. The sherardizing coatings are composed of the loose outer layer (§-FeZn13 phase) and the dense inner layer (δ- FeZn7 phase) with higher hardness. Addition of Y2O3 activator slightly increases the corrosion resistance of sherardized steel wire in comparison with CeO2. A thicker coating corresponds to a higher sherardizing temperature or a longer heating duration, but an extra thick coating is unfavorable for thru-microcrack existed in the inner layer. Good quality of sherardized wires ( higher corrosion resistance and longer duration than conditional hot-dip-galvanized one) can be produced with the zinc-rich powder containing 7.5wt.% CeO2 activator and 25wt. % SiO2 filler under 400°Cfor 6h.
Developing ecological approaches for disease control is critical for future sustainable aquaculture development. White spot syndrome (WSS), caused by white spot syndrome virus (WSSV), is the most severe disease in cultured shrimp production. Culturing specific pathogen-free (SPF) broodstock is an effective and widely used strategy for controlling WSS. However, most small-scale farmers, who predominate shrimp aquaculture in developing countries, cannot cultivate SPF shrimp, as they do not have the required infrastructure and skills. Thus, these producers are more vulnerable to WSS outbreaks than industrial farms. Here we developed a shrimp polyculture system that prevents WSS outbreaks by introducing specific fish species. The system is easy to implement and requires no special biosecurity measures. The promotion of this system in China demonstrated that it allowed small-scale farmers to improve their livelihood through shrimp cultivation by controlling WSS outbreaks and increasing the production of ponds.
Most crystalline silicon (c‐Si) solar cells are based on high temperature–processed p‐n junctions or highly doped heterojunctions. The concept of dopant‐free carrier selective contact has become a research hotspot and been successfully demonstrated with n‐type Si wafers, showing the great potential of simplified fabrication process and lower thermal‐consuming. However, there are few successful cases on p‐Si, dopant‐free p‐Si/CdS (cadmium sulfide)/ITO (indium tin oxide) solar cells with champion efficiency of 12.29% (device area 4 cm2) have been demonstrated with DC magnetron sputtered CdS thin films working as electron‐selective contact. A proper annealing treatment is found essential in improving the p‐Si/CdS/ITO heterocontact and device performance. The author's preliminary results confirm the feasibility of preparation of efficient p‐Si wafer–based dopant‐free solar cells.
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