Characterization of Polymethyl Methacrylate and Silicon Photovoltaic Cells after Processing by Laser Direct Writing Technique

Abstract

This study covers two case studies of optimizing surface modification in polymethyl methacrylate to be used as diffraction grating as well as improving efficiency in Silicon photovoltaic cell. The first aim of this work is to obtain a textured surface in Poly methylmethacrylate (PMMA), and in Silicon photovoltaic cell by means of laser direct writing machine. The second aim is the characterization of the induced surface texturing by means of Scanning electron microscopy (SEM), Raman mapping, Diffraction patterns achievement and Silicon photovoltaic's Spectral Response Measurement. In this study, a laser direct writing technique has been utilized to produce photo-thermal and optical density changes in polymethyl methacrylate surface by means of IR continuous laser and to produce micro / nano surface texture in Silicon photovoltaic cell by means of UV femtosecond laser at 180 fs, 400 nm, at 1 kHz repetition rate. The experimental evidence of the effect of femtosecond laser pulses on the spectral response of a Silicon photovoltaic cell is demonstrated and investigated. The response of this device covered the visible to near infrared spectral region. It was found that the usage of IR laser radiation (810 nm) with 0.3 Watt power was sufficient to cause significant surface damage on polymethyl methacrylate PMMA. SEM results showed formation of almost flat cracks (fissures) in PMMA sample, Raman mapping showed variations in the intensity of background scattering light in the structure of PMMA sample, no shift in Raman peaks and no new peaks appeared after irradiation process. Optical density changes caused by thermal and stress effects and plastic deformation products rather than photochemical changes may be thereby also related to refractive index modification. Laser texturing makes it possible to increase absorption of the incident solar radiation, this texturing technique produce micro/nano surface textures in Silicon photovoltaic cell by means of UV femtosecond laser pulses. The responsivity of the photovoltaic cell was increased up to 0.25A/W. In conclusions, the results summarized above showed that laser direct writing technique is fast and easy to produce PMMA diffraction grating as well as high quality Silicon photovoltaic cells. This mechanism is strongly dependant on the optical properties of the material and is recommended to be studied experimentally and theoretically in the future.