Laser Fabrication and Performance of Periodic Microstructure on Polycrystalline Silicon Surfaces

In order to reduce the reflectivity of incident light on the surface of polysilicon and improve the photoelectric conversion efficiency of solar cells,a UV nanosecond laser is adopted to prepare microdimples with different depths and pore pitch on the surface of polysilicon, and the effect of texture topography on reflectivity and photoelectric conversion efficiency is studied. The depth of the microdimples are controlled by the laser frequency while the pore pitch of the micro-dimples are changed by the arrangement of the micro- dimples. The reflectivity of polysilicon samples and surface morphology of microdimples are observed by optical fiber spectrometer and laser scanning confocal microscope,respectively; The reflection model of incident light is established using the PC1D software and the short-circuit current and open- circuit voltage of polysilicon with different pore pitch are simulated,the photoelectric conversion efficiency and fill factor are calculated subsequently. Research shows that different frequencies (300 kHz, 200 kHz,150 kHz,50 kHz)and micro-dimples arrangements (300 x 300, 310 x 310, 350 x 350, 400 x 400)have significant effects on the reflectivity and photoelectric conversion efficiency of polysilicon. As the frequency increases,the reflectivity of the polysilicon sample decreases first,then increases and finally remains stable;as the density of the lattice arrangement increases,the photoelectric conversion efficiency of the polysilicon sample gradually increases. The experiment result shows that when the laser frequency is 150 kHz and the micro-dimples distribution is 400 x 400,the topography of micro-dimples on polysilicon surface are well formed. And the average reflectivity is 3.32%,the photoelectric conversion efficiency of the polysilicon cell is 18.80%,which is 25.9% improvement compared with the untextured polysilicon cell.