OPTIMIZATION OF QUANTUM WELL PARAMETERS FOR HIGH EFFICIENCYALXGA1-XAS/GA AS SOLAR CELLS

摘要

The aim of this paper is to determine the optimum parameters associated with the use of the quantum wellfor high efficiency Alx Ga1-x As/GaAs solar cells. Two types of cells are considered, single quantum well and multiquantum wells solar cells. For the SQW solar cell, the optimized parameters are: well location in the intrinsic region,well width and aluminum mole fraction x. It is found that the optimum location of the quantum well should be awayfrom the high recombination zone around the center of the space charge region and closer to the p region. The optimumwell width is found to be 200? due to the enhancement of quantum confined Stark effect for the thick well. Molefraction of 0.2 is an optimum value taking into consideration the trade off between the open circuit voltage and the shortcircuit current. For the MQW solar cell, the optimized parameters are the barrier to well width ratio and the spacerthickness. It is found that the barrier to well width ratio should be less than 0.25 to enhance the resonant tunnellingbetween adjacent wells in order to maximize carrier collection through electron tunnelling. The optimum spacerthickness is about 300 ? to prevent the impurity scattering effect in the space charge region.