A kind of low recombination firing-through screen-printing aluminum (Al) paste is proposed in this work to be used for a boron-diffused N-type solar cell front side metallization. A front side fire-through contact (FTC) approach has been carried out for the formation of local contacts for a front surface passivated solar cell. With a low contact resistivity (ρ_c) of 1.0 mΩ·cm², good ohmic contact between the boron-doped front surface of the silicon sample and the Al paste was realized. To obtain a good energy conversion efficiency, a balance can be achieved between the open circuit voltage (V_oc) and contact resistivity (ρ_c) of the cell by combining suitable Al powders and appropriate additives. The detailed micro-contact difference in Si/metallization between the firing-through Al paste and silver-aluminum (Ag-Al) paste was analyzed. The dark saturation current density beneath the metal contact (J_{0, metal}) of the Si/metallization region using our firing-through Al paste was discussed, which was proven to be 61% lower than using Ag-Al paste. The pseudo energy conversion efficiency of the cell using Al paste measured by Suns-V_OC was also higher than using Ag-Al paste. The role of Al paste in low surface metal recombination is discussed. The utilization of this new kind of Al paste was much cheaper and more convenient, compared to the traditional process using Ag or Ag-Al paste.

Formaldehyde (FA) can exist in living cells and is involved in many physiological processes within organelles, especially lysosome, which plays pivotal roles in the FA metabolism of living systems. Therefore, a technique for the rapid and effective detection of FA is in high demand. Herein, a novel signal-on fluorometric strategy for FA determination based on Ag⁺-mediated nitrogen–sulfur co-doped carbon dots (Ag-M-NSCDs) was developed. The FA-responsive sensor was facilely prepared through introducing Ag⁺ into the lignin-derived nitrogen–sulfur co-doped carbon dots (NSCDs), accompanied by fluorescence (FL) reduction. With the addition of the FA solution, the redox interaction between Ag⁺ and FA led to the generation of Ag nanoparticles (Ag NPs) and separation of Ag⁺ from the surface of NSCDs, both of which contributed to the remarkable FL recovery. Furthermore, the fluorometric sensing system can selectively and sensitively detect FA with a linear response in a concentration range of 0–500 μM (R² = 0.997) and a low detection limit of 500 nM based on three times signal-to-noise criteria, which make the nanosensor favorable for monitoring FA in real water samples and live cells. Furthermore, it showed superior lysosomal targeting performance with a Pearson coefficient of 0.87, which demonstrates a new method for FA-related biological studies and bioanalysis.

Firing-through paste used for rear-side metallization of p-type monocrystalline silicon passivated emitter and rear contact (PERC) solar cells was developed. The rear-side passivation Al₂O₃ layer and the SiN_x layer can be effectively etched by the firing-through paste. Ohmic contact with a contact resistivity between 1 to 10 mΩ·cm² was successfully fabricated. Aggressive reactive firing-through paste would introduce non-uniform etching and high-density recombination centers at the Si/paste interface. Good balance between low resistive contact formation and relatively high open-circuit voltage can be achieved by adjusting glass frit and metal powder content in the paste. Patterned dot back contacts formed by firing-through paste can further decrease recombination density at the Si/paste interface. A P-type solar cell with an area of 7.8 × 7.8 cm² with a V_oc of 653.4 mV and an efficiency of 19.61% was fabricated.

Electrocyclizations of acyclic conjugated π-motifs have emerged as a versatile and effective strategy for accessing various ring systems with excellent functional group tolerability and controllable selectivity. Typically, the realization of 6π-electrocyclization of heptatrienyl cations to afford seven-membered motif has proven difficult due to the high-energy state of the cyclizing seven-membered intermediate. Instead, it undergoes the Nazarov cyclization, affording a five-membered pyrrole product. However, the incorporation of a Au(I)-catalyst, a nitrogen atom and tosylamide group in the heptatrienyl cations unexpectedly circumvented the aforementioned high energy state to afford a seven-membered azepine product via 6π-electrocyclization in the annulation of 3-en-1-ynamides with isoxazoles. Therefore, extensive computational studies were carried out to investigate the mechanism of Au(I)-catalyzed [4+3] annulation of 3-en-1-ynamides with dimethylisoxazoles to produce a seven-membered 4H-azepine via the 6π-electrocyclization of azaheptatrienyl cations. Computational results showed that after the formation of the key α-imino gold carbene intermediate, the annulation of 3-en-1-ynamides with dimethylisoxazole occurs via the unusual 6π-electrocyclization to afford a seven-membered 4H-azepine exclusively. However, the annulation of 3-cyclohexen-1-ynamides with dimethylisoxazole occurs via the commonly proposed aza-Nazarov cyclization pathway to majorly generate five-membered pyrrole derivatives. The results from the DFT predictive analysis revealed that the key factors responsible for the different chemo-, and regio-selectivities observed are the cooperating effect of the tosylamide group on C¹, the uninterrupted π-conjugation pattern of the α-imino gold(I) carbene and the substitution pattern at the cyclization termini. The Au(I)-catalyst is believed to assist in the stabilization of the azaheptatrienyl cation.