Synthesis, Characterization and Applications of Photoactive Nanomaterials.

摘要

In the production of some devices, novel micro fabrications techniques are important, where the goal is compatibility with the system, convenience, and cost rather than high resolution. Electron beam and photolithography techniques are common fabrication techniques used in the semiconductor industry. Even though these techniques are common, they are high cost and not compatible with many substrates. This dissertation work explores a versatile and cost effective novel technique to fabricate fluorescent active micron scale Laser Induced Structures (LIS). The optimization of the instrumental parameters and the mechanisms involved in structure formation are given, the photo-physical characterization of the LIS and a photoactive film used in solar cells is reported. Here silver nanoparticles were synthesized through a wet chemical process, concentrated and drop cast as films onto different substrates. The drop cast films were air dried and subjected to 532nm continuous wave laser irradiation to generate structures in the film. A silver nanoparticle-polymer coating formulation was also explored for structure formation and critical instrumental parameters were studied. A mechanism is proven, similar to Liquid Melt Ejection (LME), to explain the structure formation. Thermo gravimetric analysis was performed to characterize the thermal decomposition of silver nanoparticle-citrate films. In a related study, photoactive film (made out of SrAl2O4: Eu, Dy phosphor material) for solar cells was photo-physically characterized to understand its emission mechanism and was investigated against the backdrop of its effect on photovoltaic cell efficiency. A number of novel results were obtained in this work. One unexpected result relates to the structure being fluorescent active at the edges: a physical and chemical change of the material near the peak laser intensity occurred. This was attributed to light absorption and heating of the silver nanoparticles.