Optics and Photonics Society of Iran

In this paper, we have simulated and compared GaAs and InGaP single-junction (SJ) and GaAs-InGaP double-junction (DJ) solar cells, by solving Poisson, continuity and transport equations simultaneously. The comparison of solar cell spectral response proves that, GaAs and InGaP solar cells absorb wavelengths less than 873 nm and 659 nm respectively, while DJ solar cell absorbs wide range of wavelengths in the overlapped spectra. This improves the efficiency of DJ solar cell. Based on our simulation results, efficiency of GaAs solar cell and InGaP solar cell were 23.83% and 13.32% respectively; whereas, the efficiency of 30.58% was achieved by optimizing the structure of GaAs-InGaP solar cell. Furthermore, I-V characteristics of these cells showed that open circuit voltage for GaAs cell was 1 V and for InGaP cell, because of its higher band gap, was 1.4 V. This value for DJ solar cell was equal to the sum of corresponding SJ solar cell values, which was enhanced by proper design of DJ cell. By proper designing, the short circuit current was also enhanced.