Publication database
The industrial advancement of high-efficiency silicon solar cells increasingly depends on precise laser patterning and reliable silver-free metallization. For tunnel oxide passivated contact (TOPCon) devices, laser contact opening on the rear side faces a critical trade-off: achieving sufficient surface roughening for robust electroplated adhesion while minimizing thermal damage to the sensitive passivating stack. Here, we demonstrate a transformative ultraviolet femtosecond laser strategy that effectively decouples these conflicting requirements for damage-free rear-side metallization. Atomic-resolution transmission electron microscopy systematically reveals the single-pulse ablation behavior, identifying an effective SiNx removal threshold of 0.105 J/cm2 and a passivating contact damage threshold above 0.17 J/cm2, thus defining a viable processing window for selective dielectric opening with preserved electrical integrity. Building on this, we introduce a novel twin-pulse irradiation approach that exploits nonlinear energy accumulation to generate functional laser-induced periodic surface structures (LIPSS) for potential enhanced mechanical anchoring, while highly confining substrate damage to a depth of ∼30 nm. This enables ultra-narrow grid fingers (7.1 μm) and exceptionally low specific contact resistivity (0.35 mΩ cm2) in Ni electroplated contacts. These results highlight ultraviolet femtosecond lasers as a scalable, high-precision tool for next-generation silver-free TOPCon metallization, paving the way for cost-effective mass production and further efficiency gains in silicon photovoltaics.
Laser-induced graphene (LIG) enables rapid conversion of polymer substrates into conductive carbon materials. In this study, nitrogen-containing carbon nanomaterials were fabricated on polyetherimide (PEI) substrates using empirical screening of two specific process points. The resulting materials were characterized using scanning electron microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, cyclic voltammetry, and electrochemical impedance spectroscopy to correlate structural features with electron-transfer behavior. Raman and XPS analyses showed different structure and morphology depending on irradiation regime. The carbon materials with a higher sp3 fraction (≈55–59%), larger in-plane crystallite size (La up to 8.0 nm), and pronounced π–π* shake-up satellites indicated enhanced graphitic ordering when a shorter nanosecond laser was used. These structural differences resulted in substantially lower charge-transfer resistance (0.53–0.79 kΩ·cm3) and larger electroactive surface areas for the porous electrodes compared with foam structured carbon nanomaterials. The results show that, under the selected fabrication conditions, variations in laser processing parameters correspond to differences in graphitic ordering and electron-transfer properties in PEI-derived laser-induced carbon materials.
Direct-writing submicron copper circuits on glass with laser precision – without lithography, vacuum deposition, or etching – represents a transformative step in next-generation microfabrication. We present a high-resolution, maskless method for metallizing glass using ultrashort pulse Bessel beam laser processing, followed by silver ion activation and electroless copper plating. The laser-modified glass surface hosts nanoscale chemical defects that promote the in situ reduction of Ag+ to metallic Ag0 upon exposure to AgNO3 solution. These silver seeds act as robust catalytic and adhesion sites for subsequent copper growth. Using this approach, we demonstrate circuit traces as narrow as 0.7 µm, featuring excellent uniformity and adhesion. Compared to conventional redistribution-layer (RDL) and under-bump-metallization (UBM) techniques, this process eliminates multiple lithographic and vacuum-based steps, significantly reducing process complexity and production time. The method is scalable and adaptable for applications in transparent electronics, fan-out packaging, and high-density interconnects.
Teflon, or polytetrafluoroethylene (PTFE), is popular for high-frequency applications due to its low dielectric constant and high chemical resistance, but these properties also make it difficult to metallize for electronic uses because its inertness impedes metal adhesion and deposition. We present the design, simulation, and measurement of Sierpinski antenna for radio frequency energy harvesting, manufactured using the Selective Surface Activation by Laser (SSAIL) technique on flexible Teflon sheet. The results demonstrate that SSAIL is an excellent method for fabricating antennas on flexible surfaces, offering high performance and reliability. Electromagnetic simulations and experimental validations confirm the effectiveness of this approach for next-generation flexible communication devices and electronics.
In today’s electronic applications, creating accurate conductive traces on flexible transparent polymers or glass for improved functionality is crucial. These microtraces serve as integral components for transparent electrodes, heating films, and arrays of responsive sensors. Microscale circuit interposers fabricated on glass substrates are essential to advanced electronics packaging and integration. Micro and submicron scale traces fabricated straight on glass can make breakthroughs in packaging technologies. In this study, we demonstrate the capabilities of Selective Surface Activation Induced by Laser (SSAIL) technology for forming micron traces on transparent materials: glass and polyethylene terephthalate film. Trace width dependency on laser processing parameters: pulse duration, pulse pitch, pulse repetition rate, laser fluence and beam polarization are investigated. Ultrashort laser beam focused with microscopic objective is used for surface activation for selective copper electroless plating. The width of trace formed on glass can be 1.5 µm and simultaneously demonstrate supreme adhesion to the substrate.
Using laser-induced metal deposition technology, we demonstrate a cost-efficient and large-scalable method of transparent microscale metal electrode fabrication on glass. The novel electrodes are effective conductive layers, presenting a promising alternative to many electronic and electro-optic applications. This study discusses electrode formation and compares various designs. We analyzed the influence of femtosecond and picosecond laser pulse durations by varying the laser pulse duration and optimizing the repetition rate during laser processing. We found that picosecond pulses are more suitable for producing wider (about 31 μm) and higher (about 2 μm) electrodes. Meanwhile, femtosecond laser pulses are ideal for producing narrower (about 8 μm), lower (about 1 μm) electrodes. Furthermore, the optimized copper electrode design was tested in a multilayer smart window structure. It utilized a flexible conductive polymer, Poly(3, 4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS), in combination with the lithium perchlorate (LiClO4) electrolyte. We demonstrated the importance of proper layer alignment for achieving optimal smart window performance. Our findings suggest that transparent microscale electrodes formed by laser-induced metal deposition could contribute to the development of more sustainable and cost-effective smart devices.
A bendable electrode is an essential component of flexible electronics. The resistance stability against deformation is highly desired for practice. In this work, a bendable Cu electrode is fabricated by femtosecond laser direct writing (FsLDW), involving photothermal reduction of Cu ions and deposition of Cu on polyethylene terephthalate (PET) substrate. A highly conductive Cu electrode with a sheet resistance of 0.56 Ω·sq−1 is obtained, which is improved by at least one order of magnitude over previous works. It is worth noting that the sheet resistance of the Cu electrode almost remains unchanged after 6000 downward bending cycles at a bending angle of 30° and shows a slight increase after 10 adhesion tests, demonstrating excellent bending stability and adhesive strength. The porous morphology of the deposited Cu may relieve bending stress, resulting in high deformation resistance. The temperature field simulation confirms sufficient heat accumulation during FsLDW for Cu ion reduction and PET surface melting, allowing for Cu embedding on the PET surface and improving adhesion between the Cu electrode and the substrate.