Preparation And Properties Of Nip-type Amorphous Silicon Thin Film Solar Cells

In view of the shortage and price rising of silicon raw materials, the amorphous silicon (a-Si) film solar cells have been increasingly concerned by the governments over the world due to their less material consuming, lower cost and greater potential for performance enhancement. In this paper, based on the fabrication of the n-i-p type a-Si solar cells, we mainly focused on the performance of cells in association with the substrate morphology, structure of back reflector and related process conditions of window layer.Firstly, a novel quasi-periodic nanodent Al substrate was introduced into n-i-p type a-Si solar cell and its performance was compared with that of cells based on the commercial F doped SnO2(SnO2:F, FTO) transparent conductive glass substrate (Asahi ANS14) and flat substrate. The results show that, in the wavelength range of500-800nm, the cells on nanodent Al substrates obtain the highest External Quantum Efficiency (EQE) spectral response. And the short circuit current density and photoelectric conversion efficiency are also higher than that of other two cells. It assumes that the light trapping capability of the nanodent Al substrate is better even than that of commercial FTO substrate.Secondly, based on the nanodent Al substrates, the back reflectors with three different structures have been designed for the n-i-p type a-Si solar cells. Obvious differences in short circuit current density for these solar cells are observed. And then a new back reflector structure has been designed for our future works according to the conclusions analyzed above.Thirdly, by analyzing the results characterized above, we realize that Al doped ZnO (ZnO:Al, AZO) spacer layer plays an important role in the light trapping effect. Therefore, the relationship between the AZO thickness and the performance of cells on nanodent Al substrate has been further investigated by combining the Finite-Difference Time-Domain (FDTD) simulation and experiment methods. The simulation and experiment results display that tuning the AZO thickness can change the inner electric field distribution of cells and effect obviously on short circuit current density (Jsc), open circuit voltage(Voc) and fill factor (FF). At last, the optimized solar cells are obtained as100nm AZO employed.Fourthly, considering that the performance of solar cells is sensitive to the properties of window layer, we optimized the doped concentration, thickness and deposition temperature of p layer and thus enhanced the cells’performance.Finally, the highest photoelectric conversion efficiency of cells based on nanodent Al substrate is up to8.2%by the previous optimizing of some certain process conditions. And the light induced effect of the cell also has been investigated preliminarily by subjecting the cell to200hours light soaking. A decrease of7.41%in.JSC is observed and the final stable efficiency of the cell is still as high as7.44%.