Morphology And Optical Properties Controlling For The Surface Of Poly-crystallized Si Used In Solar Cell By Technique Parameters

Solar energy is a new green energy with the advantages of inexhaustible, clean and renewable to deal with the global energy crisis. So it has become the focus of attention. Solar cells, which is an effective device based on photovoltaic effect to utilize the solar energy, have become an important direction of research and application on the energy now. This thesis studies the light trapping effect of crystalline silicon solar cells, the main results are summarized as follows:This thesis studies the silicon etching process in liquid HF-HNO3-H2O acid etching system. The main researches are the removal of the surface damage layer, and the effects of etching time, acoustic (ultrasonic) and magnetic field on the surface structure and optical properties. The experiment results show:the reaction rate in the rich HF system is stable and easy to control the reaction process, the suede is covered by craze. This is because the concentration of HNO3 in the rich HF system is low, the reaction occurs in the regions of the low activation energy, such as crystal defects. The poly-silicon antireflective effect of HF secondary corrosion for suede is better than that of HNO3 secondary corrosion. And the suedes etching in the condition of acoustic (ultrasonic) and followed by HF secondary corrosion have more excellent antireflective effect. As the corrosion time increases, surface morphology changes gradually from the micro-crack to the bubble, the reflectance decreases at first and then increases; the magnetic field does not affect the variation of the suede morphology and reflectivity with time, but changes effectively the surface structure and light trapping effect. Experiments also show, when the corrosion time is 2 to 3min, the ratio of depth to width of the crack pits is the best and light trapping effect is more wonderful; surface light reflectivity of the suede produced in the magnetic field can be down to about 5%, a third of that without magnetic field, this is because that magnetic field suppresses the horizontal action and develop the vertical action, which promote the formation of the porous silicon.This thesis also studies the photoluminescence spectra of the suede produced in the magnetic field, compared with the traditional suede, it luminescence the light of 550-750nm in the experiment, consistent with the photoluminescence peak of porous silicon in the other literatures. XPS measurements show that acid etching and external magnetic field change the silicon and oxygen ratio, the magnetic field lead to the increase of O content. In addition, the photoluminescence lifetime of the annealing suede produced in the magnetic field is shortened by measuring time-resolved fluorescence. The results show that the structure of suede with external magnetic field is mainly the porous silicon structure.