We demonstrate single-order operation of Lamellar Multilayer Gratings in the soft x-ray spectral range. The spectral resolution was found to be 3.8 times higher than from an unpatterned multilayer mirror, while there were no significant spectral sideband structures adjacent to the main Bragg peak. The measured spectral bandwidths and peak reflectivities were in good agreement with our theoretical calculations

Lamellar Multilayer Gratings (LMG) offer improved resolution for soft-x-ray (SXR) monochromatization, while maintaining a high reflection efficiency in comparison to conventional multilayer mirrors (MM). We previously used a Coupled-Waves Approach (CWA) to calculate SXR diffraction by LMGs and identified a single-order regime in which the incident wave only excites a single diffraction order. We showed that in this regime the angular width of the zerothorder diffraction peak simply scales linearly with Γ (lamel-to-period ratio) without loss of peak reflectivity. However, the number of bi-layers must then be increased by a factor of 1/Γ. Optimal LMG resolution and reflectivity is obtained in this single-order regime, requiring grating periods of only a few hundred nm, lamel widths < 100nm and lamel heights > 1μm [1]. For the fabrication of LMGs with these dimensions, we use a novel process based on UV-NanoImprint Lithography (UV-NIL) and Bosch-type Deep Reactive Ion Etching (DRIE). Successful fabrication of LMGs with periods down to 200nm, line widths of 60nm and multilayer stack heights of 1μm is demonstrated. SXR reflectivity measurements were performed on these LMGs at the PTB beamline at the BESSYII synchrotron facility. The measurements demonstrate an improvement in resolution by a factor 3,5 compared to conventional MMs. Further analysis of the SXR reflectivity measurements is currently being performed.

An industry-ready strategic process for the fabrication of cost-effective, micropatterned Ni–Cu–Sn front contact metallization has been demonstrated using maskless direct-write lithography, which could effectively reduce the shadow loss and thereby enhance the efficiency of silicon solar cells by increasing the active area. This investigation also addresses the challenging issues in Ni–Cu–Sn metallization, such as adhesion of the seed layer, low-ohmic contact formation, background plating, and cell processing complications. An eco-friendly aluminum paste with a sheet resistivity of 35 mΩ/cm2 has been developed to fabricate the rear contact on silicon solar cells. A front contact metallization grid with an optimal narrow finger width of 20 μm with an interfinger spacing of 1000 μm has been micropatterned using maskless direct-write lithography for the metallization process. To improve the electrical and mechanical properties of the nickel seed layer, the thickness was optimized as ∼100 nm with a contact resistivity of 6.87 μΩ cm2, which exhibited an adhesion strength of 2.5 N/mm. A low ohmic contact intermediate silicide layer has been created at the Ni–Si interface by the rapid thermal annealing process at 420 °C for 90 s with subsequent copper and tin electroplating to form the Ni–Cu–Sn contacts. An average cell efficiency of 18.5% is achieved for silicon solar cells with a micropatterned Ni–Cu–Sn-based narrow line-width front contact grid design, which could exhibit an ∼1% cell efficiency enhancement as compared to commercial Ag screen-printed solar cells. An ∼6% improvement in cell performance is achieved by reducing the shadow loss with the Ni–Cu–Sn-based front contact metallization as compared to the commercial Ag screen-printed metallization.

Herein, a systematic investigation on the design and development of a cost‐effective nickel hard stamp suitable for fabrication of a new front‐side metallization pattern to reduce the shadow losses in solar cells is demonstrated. Finite element analysis (FEA)–based simulations indicate an optimal finger width of ≈20 μm with interfinger spacing of 1000 μm which can effectively enhance solar cell efficiency by ≈1% due to reduced shadow loss. The optimal grid design is further patterned by means of nanoimprint lithography (NIL) followed by an electroless deposition method. A cost‐effective, electroless deposited nickel hard template is developed for NIL patterning using UV pattern transfer. To avoid the physical damages during the imprinting process and improve the durability of the NIL stamp, silane‐based antiadhesive coating is used which can withstand up to 18 cycles of imprinting process. The nickel hard stamp exhibits improved hardness of 5.63 GPa and roughness of 8 nm and is used to transfer the narrow‐line width patterns during the imprinting process. The proposed industry‐ready technology overcomes the limitations of the existing screen printing process pertaining to the formation of high‐aspect‐ratio narrow line‐width finger grid patterns.

An in‐house‐developed nanoimprint lithography system is designed and developed to demonstrate a commercially viable method for creating Ni–Cu–Sn‐based narrow linewidth finger patterns capable of effectively reducing shadow loss in the front contact metallization on industrial silicon solar cells. Finite element analysis simulation studies estimate that an optimal force of 138 MPa is required to generate damage‐free patterns during nanoimprinting process. The poly (methyl methacrylate) residual layer is removed using reactive ion etching, which enhances the adhesion strength of Ni–Cu–Sn metallization. A low ohmic contact layer at the Si/Ni interface develops after sintering at 420 °C and formation of NiSi layer is confirmed through X‐ray photoelectron spectroscopy analysis as a function of Ar+ ion etching time. An average cell efficiency of 18.10% is achieved for silicon solar cells with micropatterned Ni/Cu/Sn‐based narrow linewidth front contact grid design, which can exhibit ≈1% enhancement in cell efficiency compared to commercial Ag screen‐printed solar cells. The Ni/Cu/Sn‐based front contact metallization can improve the cell performance by ≈6% compared to the commercial Ag screen‐printed metallization by reducing shadow loss and thereby indicating its suitability toward deploying for cost‐effective industrial solar cell manufacturing.