Abstract
This thesis is studying the fabrication and analysis of a-Si/c-Si hetero-junction solar cell by using ion implantation technique, and the study of ITO ARC-layer ( anti-reflectance coating ) optimization. We use LPCVD to deposit i-a-Si on n-c-Si wafer, and use ion-implantation technique to form emitter-layer ( p+-a-Si ) and BSF ( back surface field, n+-a-Si ), this technique is quick than diffusion method. And a-Si has good passivation property at a-Si/c-Si interface, can reduce the dangling bonds at the interface, and increase the short-circuit current ( Jsc ) apparently. This thesis has four main experiments. First, we try to find the better process conditions of ITO by different sputter power and vacuum annealing. Afterwards, we analyze the electric property, optical property, and the crystallinity of ITO thin-film. By our investigation, we find the better process conditions of ITO is 110W sputter power and 400℃ 30min vacuum annealing, and the ITO has the best property for ARC-layer of solar cell. The sheet resistance is 42 Ω/square, transmittance is 91.57% and reflectance is 14.59% for the optimized ITO. Second, we fabricate the optimized ITO ARC-layer on a-Si/c-Si solar cell, the Jsc is improved from 34.44 mA/cm2 to 35.44 mA/cm2, FF is improved from 0.629 to 0.694 significantly, and the efficiency is improved from 11.71% to 14.01% due to the reduction of lateral resistance. Third, we doping emitter layer of solar cell with BF2 or B source by ion implantation with ITO optimization. We find the efficiency of solar cell will be enhanced with BF2 source because Jsc and Voc is improved slightly due to the reduction of defects at a-Si and a-Si/c-Si interface by fluorine passivation. Forth, we can observe tilt ion implantation can achieve better shallow junction by SRIM simulation. From the theory of solar cell, we know shallower junction can get better Jsc and conversion efficiency will be enhanced. Hence, we dope emitter layer by 60o-tilt ion implantation with BF2 source. Afterwards, SIMS analysis can prove the tilt ion implantation can achieve better shallower junction certainly. By our investigation, we observe that Jsc is improved from 35.44 mA/cm2 to 36.85 mA/cm2 significantly, and the efficiency is improved from 14.01% to 14.41% by 60o-tilt ion implantation due to the better shallower junction. In this thesis, we have achieved the better solar cell conversion efficiency of 14.41%, Jsc of 36.85 mA/cm2, Voc of 0.565V and FF of 0.692 ( AM1.5, area=1cm2 ) by ITO optimization and 600-tilt ion implantation with BF2 source.