Design of High Efficiency lnxGa1-xN-Based Multi-Junction Solar Cells

Abstract

Photovoltaic (PV) power generation is becoming widespread as a clean and gentle energy source for the earth. The main drawback of currently used photovoltaic cell is its low conversion efficiency and materials with the appropriate band gaps that can perfectly match the broad range of solar radiation. Recently it has been shown that the energy gap of 1nGa1 N alloys potentially can be continuously varied from 0.7 to 3.4 eV, providing a perfect matching to the full-solar-spectrum. Therefore, InGa t N becomes a promising material for very high efficiency multijunction solar cell. Any desired value of bandgap can be obtained from this material choosing the appropriate composition. In this work, InGa.N-based multijunction solar cells have been designed theoretically for high efficiency and the performance of the designed solar cells are evaluated with various parameters. The theoretical design and performance evaluation are done by developing a simulation model. The developed mode optimized the solar cell design for high efficiency at different junction numbers. The efficiency is found to be varied from 24.49 to 45.35 % for single junction to eight junction solar cells. The current mismatches of multijunction solar cell are kept within 0.29%. The lattice mismatches between different cells were found to be varied from 0.86 to 3.15%. The increase in surface recombination velocity and emitter thickness decreases the efficiency. On the other hand, the increase in minority carrier lifetime of emitter and base, and doping density increase the efficiency. In order to get more accurate results the effect of depletion width was taken into account. However, no significant change is observed between the results without and with considering le depletion width. The performance of InGaN-based MJ solar cells under concentrator is studied. The efficiency is found to be varied from 24.49 to 39.28 (%) for single junction and 45.35 to 72.79 (%) for eight junction, without and with concentrator. respectively. This model can be applied to design the solar cells at any number of junctions.