Preparation Of Aluminum Nanometer Pits And Its Application In Solar Cells

The research content of this thesis is divided into two parts. The first part is the study of fabrication and light scattering properties of size controlled aluminum nanopits. Aluminum (Al) nanopits are fabricated by electrochemical oxidation and wet chemical etching method in oxalic acid, phosphoric acid, and citric solution. The average diameter of the Al nanopits texture can be controlled by tuning the chemical parameters of the oxalic acid, phosphoric acid, and citric acid solution under the different applied voltages from40V to310V. In addition, the effects of electrolyte concentration and applied voltage on the average diameter and average depth of the aluminum pits are studied. And the reflection and scattering properties of Al nanopits texture are investigated by using UY-VIS-NIR Spectrophotometer, light scattering instrument, and the finite-different time-domain (FDTD) method. The second part is the application of Al nanopits texture in solar cells. By using the FDTD method and the conclusion of the first part, we design amorphous silicon thin film solar cells on flexible substrates and optimized the average size of nanopits on flexible Al substrates. In addition, we fabricate the amorphous silicon thin film solar cell by plasma enhanced chemical vapor deposition apparatus (PECVD) on the flexible Al nanopita textured substrate. The optical performance of the solar cell is analyzed by a current-voltage (J-V) and quantum efficiency (QE) test. The conclusions obtained are as follows:(1) By tuning the electrochemical parameters, average diameter of the Al nanopits can be controlled from0.06um to over1.08μm.(2) Under the applied voltage of280V, the influence of the electrolyte concentrat-ion of citric acid on nanopits average diameter is relatively small. And a maximum nanopits average diameter of760nm is obtained in2%citric acid solution.(3) The average diameter and depth of Al nanopits increase obviously with the increase of applied voltage. And the variation range of average diameter is larger than that of the average depth with the increase of applied voltage.(4) The reflectance decreases with the increase of the nanopits average diameter on the surface of Al texture. Under the incident wavelength of636nm, the light scattering intensity become stronger with the increase of average diameter of the nanopits on the surface of Al texture and become weaker as the scattering angle increases.(5) By using the commercial software Lumerical Solutions based on the3D finite-difference time-domain (FDTD) method, the near-field and far-field properties of the Al nanopits are investigated. The calculation results indicate that the near-field intensity of Al nanopits texture become weaker while the far-field scattering of Al nanopits texture become stronger with the increase of the nanopits average diameter under the incident wavelength of636nm. With the increase of the average diameter of Al nanopits, the far-field scattering increase gradually and tends to a large angle and long wavelength range in the wavelength range of400nm to800nm.(6) By using FDTD method, we optimize the best size of Al nanopits texture as back electrode of solar cell and the best size is1080nm. The aluminum back electrode with periodic nanopits texture can effectively improve the absorption of the amorphous silicon solar cells at the wavelength range of200nm to1100nm, and the total absorptivity increase16%.(7) Compared with the amorphous silicon thin film solar cells whose back electro-de is polished aluminum substrate? the performance of the amorphous silicon thin film solar cells with Al nanopits texture back electrode have been improved. The short-circuit current density is increased by8%, fill factor by1.69%, and the efficiency by0.59%.