Mechanism And Experimental Study Of Enhancement Absorption Of Solar Cells

With the decreasing of fossil fuels resources and the increasing of environmental contamination caused by fuels combustion emission, the exploration of clean and renewable energy becomes one of the most pressing human needs, one of which is the solar energy which has become the most promising renewable and clean energy because of its huge reserves and wide geographic distribution. But compared to the fossil fuel industry at present, solar related industry such as solar cell still has some disadvantages, because its two critical issues of high cost and low efficiency block its wide application. The study found that the absorption characteristics of solar cell can be effectively improved by controlling the structural morphological characteristics of the surface structure, meanwhile the optical loss reduced and the conversion efficiency enhanced. With the rapid development of the micro-fabrication technology in recent years, the problem of micro-structure surface spectral control has attracted attention and has important value in engineering application. Based on above this dissertation will give exploration to the enhancement of optical absorption and experimental study of solar cells surface micro-structure using micro-fabrication technology. The main contents are listed as follow.1. Solar cells theory and numerical calculation methodsFor the physical process of photons absorbed and electron-hole pairs generated, micro-structure model of solar cells is founded based on electro-magnetic theory; the interaction between the incident light and solar cells is described by Maxwell’s equations, which are discreted with finite-difference-time-domain (FDTD) method, and the numerical calculation methods are established.2. Enhancement absorption mechanism and optimization of monocrystalline silicon solar cellsThe interaction between the incident solar light and the surface of the cell is analyzed based on the electromagnetic theory. The finite difference time domain method (FDTD) is used to discuss the surface spectral absorption characteristics of monocrystalline silicon solar cell in work band. The influence of partial type, structure parameters, temperature on spectral characteristics of one-dimensional monotonic grating surface is discussed. For monotone grating absorption characteristics limitations, one-dimensional assembly grating structure is considered and the absorptivity is improved efficiently. According to the results, the enhancement absorption mechanism is revealed. In addition, two-dimensional nano-column array is used to enhance the light capture, and the effect of microstructure parameters on spectral properties is investigated. Based on the method of the ideal short-circuit current density of solar cells, the ideal efficiencies of one-dimensional monotonic grating, one-dimensional assembly grating and two-dimensional nano-column are calculated under AM1.5spectral.3. Enhancement absorption mechanism and optimization of silicon thin-film solar cellsConsidering the influence of electrodes and intrinsic absorption layer, the calculation model of spectral characteristics of a-Si:H thin film solar cell is established. Its spectral characteristics are simulated, and the influence of material and structure parameters on which is investigated. For silicon thin-film solar cell structure, its internal resonance is analyzed based on Fabry-Perot (FP) mode. To enhance absorptivity, a new a-Si:H thin-film solar cell structure is proposed, which effectively improve absorptivity of the a-Si:H thin film solar cell in short wavelength. The material properties, nanoparticels size and position on absorption characteristics is analyzed. Moreover, back antireflective structure and composite antireflective structure are studied.4. Experimental study on enhancement absorption of silicon solar cellsThe silver film on the surface of silicon wafer is firstly prepared by magnetron sputtering, and then the silver nanoparticles are made by anneal process. Based on inductively coupled plasma etching techniques (ICP), the nano-cone structure is created, and also the effect of etching time and power on nano-cone structures formation is analyzed. The surface morphology is surveyed with scanning electron microscope (SEM), and the full wave-band optical spectrum is measured through Ultraviolet-Visible-Infrared spectrophotometer. The coordinates of designated points on microstructure is obtained by atomic force microscopy microstructure (AFM), and the surface spectral curve is simulated with finite difference time domain (FDTD) method, which is compared with experiment results to verify the rationality of the method.