Search

Laser-induced graphitic carbon (LIGC) is a promising technology to manufacture conductive carbon in a cost-effective manner on a flexible substrate with a scanned laser. One limitation preventing the widespread adoption of LIGC in electronic devices and circuits has been its relatively high sheet resistance. Here, we report the lowest sheet resistance to date for LIGC engraved on flexible polyimide of 6.14 ± 0.11 Ω/□. Several general strategies are identified to minimize sheet resistance. Most importantly, the total laser energy per unit area delivered to the substrate needs to be maximized. This can be achieved by increasing laser power, decreasing laser scan speed and increasing overlap between adjacent pulses. Pulse overlap can be increased by increasing linewidth (raster rather than vector mode) and increasing the dots per cm resolution, i.e., decreasing spacing between pulses, which also improves LIGC uniformity. Further, decreasing scan speed increases the ablation threshold because of increased cooling between pulses enabling more energy to be delivered without the material ablating. These insights were obtained using a combination of electrical measurements, thermal modeling and material characterization. With optimized energy delivery, a domain size (La) of about 60 nm was obtained, which highlights the high quality of the obtained LIGC material.

Exploring the underwater solar energy by solar photovoltaic (PV) cells leads to a huge advantage by utilizing the humongous space of water covered by the earth's surface. Even though the amount of solar radiation decreases with the depth of the water, water provides sustainable cooling and cleaning for solar PV cells underwater. There are many challenges and constraints to develop solar PV cells underwater because they are mostly calibrated and amenable to space, dryland, terrestrial, etc., and the solar spectrum is prone to get narrower with the depth of the water. The implementation of solar PV cells underwater is pliable in various commercial and defense applications, such as sensors, water monitoring systems, autonomous vehicles, underwater gliders, etc. In this article, first, a mathematical model has been developed for the solar cell spectrum to incorporate the changes in the solar irradiance with the depth of the water. Furthermore, an experimental setup was designed and implemented to mimic an underwater environment. The performance of the polycrystalline encapsulated solar cell was studied based on the different types of water and the depth of the solar cell underwater. This article manifests that there is a sufficient amount of underwater solar power that can be utilized using PV cells to operate various devices and systems.