The spectral variation effects on energy yield of optimized multi-junction solar cell

The effect of spectral variations on the maximal achievable efficiency of multi-junction solar cells is investigated in this paper. The energy yield rather than power rating are considered here. With the optimized band gaps under STC the average and annual efficiency for spectral irradiances measured at CREST in a wavelength range from 310-1710 nm is calculated. The material band gap optimised for the measured average annual spectrum and for STC spectrum are compared. The annual efficiency and the annual yield of multi-junction solar cells are calculated. It shows that optimum material band gaps shift for a spectrum deviates from AM1.5 which indicates that the spectral effects should be taken into account to optimize multi-junction solar cell structure and system design. The energy generated in Loughborough is calculated for one year and it is shown that the performance ratio of multi-junction solar cells optimized under realistic condition is significantly reduced.