Study On The Poly-Si Thin-film Solar Cells On Glass And The Back Reflectors

As a kind of new energy, solar energy receives widespread attention around the world tosolve the crisis of fossil energy and to alleviate the pollution of environmental. Solar cells areconsidered the main route of solar energy utilization. In view of the global demand, the supplyof raw material, preparation process and the material properties, polycrystalline siliconthin-film solar cells on glass will have good prospect. Recently, due to the use of lighttrapping and other influences, photonic crystals, especially one dimensional photonic crystalshave been generally applied to thin-film solar cells.We provid a brief description of solar cells research background, and make presentationfor the development situation of solar cells and have an in-depth analysis of the principle ofphotovoltaic power generation and the relevant performance parameters. Besides, traditionalback reflectors and photonic crystal have also been given a detailed analysis. And then, thetopic support and the main research content are put forward.The device simulation of polycrystalline silicon thin-film solar battery is carried out bysolar cells simulation software PC1D. The solar cell is divided into several regions for theconvenience of independent studies of each layer. We give a systematic analysis on therelations between output performance of the solar cell and the associated parameters of base,emitter and back surface field (BSF), surface recombination rate and back reflectance. Theresults show that the base doping concentration, thickness and minority carrier diffusionlength make a significant impact on the photoelectric properties of solar cells. And the bestbase doping concentration is1.39×1016cm-3. Though thickening the thickness of base wouldbe beneficial to absorbing photons, the thickness is not the thicker the better, it is limited bythe base minority carrier diffusion length. When the ratio between the base minority carrierdiffusion length and the base thickness is about1under a certain electrical quality, theperformance is best. The impact of back surface recombination rate is much more remarkablecompared with the front, and the effect of the improvement of the base minority carrierdiffusion length is superior to that of decreasing surface recombination rate. The thinner theemitter, the better to collect minority carrier. And the doping concentrations of emitter and BSF layer also have a major impact on solar cell conversion efficiency. Selection of thethickness of BSF layer would also depend on its minority carrier diffusion length. Increasingback reflectance is another way to enhance photoelectric conversion efficiency.A different set of one-dimensional photonic crystals are prepared by ion beam sputteringtechnique with sputtering the selected two kinds of dielectric materials Si and TiO2alternately.We study the impact of associated parameters of one-dimensional photonic crystals on thereflection performance, such as the odd or even structure, cycles and lattice constants.Because of the absorption loss, the same periodic one-dimensional photonic crystals witheven layers work best. But the numbers of layers are not the smaller the better,one-dimensional photonic crystals need maintain a certain structure, the optimal number ofcycles is3. The surface morphology graphs show the difference between the surfaceroughness is small, so the scattering loss is not taken into account and the absorption lossplays an important role in the difference between reflection performance. The location andmagnitude of reflection peaks would change with the lattice constants and filling rate. As awhole, the influences of the associated parameters on one-dimensional photonic crystalsindicate that for the one-dimensional photonic crystals composed of Si and TiO2, the sampleworks best and the highest back reflectance could reach84.8%in the range from550nm to1100nm, when the thickness of Si is50nm and that of TiO2is80nm, the period is3and thetotal number of layers is6.