The effects of ion doses on the properties of boron implanted Si for n-type solar cell application were investigated with doses ranging from 5×1014cm-2to 2×1015cm-2and a subsequent two-step annealing process in a tube furnace.With the help of the TCAD process simulation tool, knowledge on diffusion kinetics of dopants and damage evolution was obtained by fitting SIMS measured boron profiles. Due to insufficient elimination of the residual damage, the implanted emitter was found to have a higher saturation current density(J0e) and a poorer crystallographic quality. Consistent with this observation, V oc, J sc, and the efficiency of the all-implanted p+–n–n+solar cells followed a decreasing trend with an increase of the implantation dose. The obtained maximum efficiency was 19.59% at a low dose of 5×1014cm-2. The main efficiency loss under high doses came not only from increased recombination of carriers in the space charge region revealed by double-diode parameters of dark I–V curves, but also from the degraded minority carrier diffusion length in the emitter and base evidenced by IQE data. These experimental results indicated that clusters and dislocation loops had appeared at high implantation doses, which acted as effective recombination centers for photogenerated carriers.
The optimizations of the emitter region and the metal grid of a concentrator silicon solar cell are illustrated. The optimizations are done under 1 sun,100 suns and 200 suns using the 2D numerical simulation tool TCAD software.The optimum finger spacing and its range decrease with the increase in sheet resistance and concentration ratio.The processes of the diffusion and oxidization in the manufacture flow of the silicon solar cells were simulated to get a series of typical emitter dopant profiles to optimize.The efficiency of the solar cell under 100 suns and 200 suns increased with the decrease in diffusion temperature and the increase in oxidation temperature and time when the diffusion temperature is lower than or equal to 865℃.The effect of sheet resistance of the emitter on series resistance and the conversion efficiency of the solar cell under concentration was discussed.
The silicon vertical multi-junction(VMJ)solar cell has a good potential in high concentration,but it requires high quality front and back surface passivation layers to keep its high efficiency.We try to add dopants into the front and back surfaces of the VMJ cell to release this strict requirement in this work.The effects of recombination velocities,doping types and doping profiles of front and back surfaces on the performance of the P-type VMJ cell were calculated under 1 sun and 1000 suns.The 2D numerical simulation tool TCAD software was used.The performance of the VMJ cell without front and back surface dopants was also calculated for comparison.It was found that the requirement of high quality front and back surface passivation layers could be released remarkably by adding either N-type or P+-type front and back surface dopants.For the two types of front surface dopants,the highest efficiencies of the cells were got by light dopant;for the two types of back surface dopants,the doping type and profile affected little on the performance of the cell in our calculation range.It was also found that the series resistance of the VMJ cell with N-type front surface dopant was decreased by the 2D effect of front surface emitter.The VMJ cell with P+-type front surface dopant had the highest efficiency under 1000 suns and the VMJ cell with N-type front surface dopant had the highest efficiency under 1 sun in our calculation range.
