Clean Technology 2007
M. Halbwax, T. Sarnet, Ph. Delaporte, M. Sentis, H. Etienne, F. Torregrosa, V. Vervisch and S. Martinuzzi
LP3 UMR CNRS 6182, FR
photovoltaic, femtosecond laser, black silicon, plasma immersion
It has been shown in a recent past (Mazur et al) that a simple way to improve the silicon-based solar cells low efficiency (around 20%) is to irradiate the silicon surface with a series of femtosecond laser pulses, in the presence of a sulfur containing gas. This improves the formation of micro-spikes on the silicon surface that strongly absorbs the incident solar light (Black Silicon). We have in this paper studied the influence of other irradiation conditions like the laser pulse duration (femtosecond and picosecond), polarization and beam shaping of the laser, scanning parameters and background pressure rather than gas composition. The results show how it is possible to create different types of Black Silicons with absorbing spiked structures when playing with these parameters, leading to totally different optical properties and photovoltaïc efficiencies. Demonstrator devices are shallow emitter solar cells on N type polycristalline silicon. To cope with the 3D structured front surface made by femtosecond laser treatment, doping of emitter is realized by using Plasma Immersion Ion Implantation (PULSION tool developed by IBS). Classical furnace and Laser Annealing (193nm) are tested to activate the shallow 3D junction. Spectral answer and yield of the obtained solar cells are presented.