Based On The Amorphous Silicon Thin Film Solar Cell Experiment And Simulation

Compared with crystalline silicon solar cells, thin film solar cells based on hydrogenated amorphous silicon (a-Si:H), are well known as being of simpler process, lower cost and less energy consumption. However, due to the defects in the structure and the light-induced degradation of a-Si:H thin films, the stability and conversion efficiency of the thin film solar cells are still not satisfied, resulting in the failure of large-scale application.There are two factors that affect the conversion efficiency of the solar cells based on a-Si:H thin films. One is the material’s property itself and the other is the structure of solar cells. In this thesis, in order to optimize the thin film’s properties and the structure of solar cells based on a-Si:H thin films, some fundamental experiment studies were carried out on different aspects such as the pre-treatment of transparent conductive oxide (TCO) surface, the structure and performance characterization of a-SiC:H thin films, and the electrically contact ability of TCO/p heterojunction. Then, the functional properties of the solar cells based on a-Si:H thin films were simulated using a software named as AMPS-1D. The main results are shown as follows.(1) The surface of AZO glass treated by hydrochloric acid is textured, and the optimum texture can be obtained when the specimens were treated by20seconds. The surface of ITO glass treated by concentrated sulfuric acid goes rough at early stage, but declines later, with the increase of treating time. This indicates that contaminant and Sn oxides are successfully eliminated, so that the surface becomes smooth and the work function increases, resulting in the improvement of cells’performance.(2) With the increase of CH4flow ratio in the gas mixture, the deposition rate of a-SiC:H thin films decreases. The results of FTIR test show that the number and strength of C-C and Si-C bonds in the a-SiC:H films are increased with the increase of CH4flow ratio. The optical band gap of a-SiC:H thin films deduced by UV-visible spectroscopy is increased with the increase of CH4flow ratio.(3) Concerned the electrical contact of AZO/a-SiC:H heterojunction, there is an optimum time after the surface of AZO galss is textured by20seconds with the dilute hydrochloric acid. The ohmic contact of ITO/a-SiC:H heterojunction is obtained when ITO is treated by10minutes or by15minues with concentrated sulfuric acid. The contact of FTO/a-SiC:H heteroj unction is intrinsically ohmic, and the contact resistance is less than that of untreated AZO/a-SiC:H heteroj unction. The CH4flow ratio in the deposition of a-SiC:H thin films has a heavy influence on the contact ability of TCO/a-SiC:H heteroj unction, and the smaller the flow ratio, the better the electrical contact.(4) The results of simulation indicate that the performance of the cells based on a-Si:H thin film can be improved efficiently with the increase of ITO work function. There will be an optimum performance in the cells when the thickness of p-layer is set as10nm, the optical band gap of a-SiC:H thin film is among2eV～2.2eV and the doping concentration is slightly more than1×1020/cm3. The thickness of i-layer and the density of defect states in it play a key role in the performance of the cells. The optimum i-layer thickness is about600nm under which the density of film defects can significantly be reduced and the performance of the cells based on a-Si:H thin films can be greatly improved.