Computational investigation to improve the External Quantum Efficiency of thin film tandem solar cell

A thin-film tandem solar cell is designed from two different semiconductors in order to observe the impact of thickness of active layers on External Quantum Efficiency (EQE) by keeping the anode voltage fixed for both top and bottom cells. A nearly lattice matched ZnO-Si hetero-structure thin film device has been simulated to get the maximum EQE at a particular wave length. For the anode voltage of 5V, at a thickness of 8 nm of the active layer, we obtained a EQE of 0.936 for the top cell and for the bottom cell the optimized value of EQE is 0.819 at a thickness of 14 nm. The optimized values of EQE for both the cells were obtained at a wavelength of 460 nm and 674 nm respectively. In this regard, the impact of thickness of active layers on V-I characteristics of thin film tandem solar cell were observed.