Development of high-performance solar cells using solar spectrum splitting technique

To increase the performance of solar cells, solar spectrum splitting technique has been considered and studied. It was found from the simulation that the total efficiency of nearly 25% can be obtained at the splitting wavelength of 600 nm for thin-film type solar cell using a-Si and CIGS as the top and bottom cells, respectively. The experiment has been carried out to verify the simulation results. By the optimization of device and splitter, up to now the total efficiency of about 22 % has been obtained at the splitting wavelength of 620 nm which is similar to the simulation results. Further work has been done using InGaP as the top cell instead of a-Si. Up to now an high efficiency of 26% has been measured for InGaP//CIGS configuration using the developed spectrum splitting technique. Higher performance can be expected with c-Si bottom cell or under concentration application. For higher cell efficiency, the configuration using InGaP//GaAs//CIGS using 2 optical splitters has been considered and its potential efficiency has been calculated. It was found that the maximum effiency of more than 30% can be expected with this configuration.