Theoretical Analysis of Two-Terminal and Four-Terminal Perovskite/Copper Indium Gallium Selenide Tandem Solar Cells

Perovskite/copper indium gallium selenide (CIGS) tandem solar cells represent an attractive configuration to obtain ultrahigh efficiency. A detailed theoretical analysis is crucial for further improving the performance of tandem solar cells. Herein, four-terminal and two-terminal perovskite/CIGS tandem solar cells are intensively researched. For four-terminal perovskite/CIGS tandem solar cell, the optimal thicknesses of CH3NH3PbI3 and CIGS are 0.5 and 3 mu m, respectively, according to the simulation result. Reducing the thickness of TiO2 and Spiro-OMeTAD can minimize the short-wavelength parasitic absorption and long-wavelength parasitic absorption, respectively. Meanwhile, using antireflection coating, such as 100 nm MgF2, is beneficial to increase the photon absorption. For two-terminal perovskite/CIGS tandem solar cells, the thicknesses of perovskite and CIGS are tuned to meet the current matching. To further improve the efficiency of two-terminal tandem cells, FTO thickness is reduced to minimize reflection, and the optimal doping concentration of CIGS (1 x 10(18) cm(-3)) is used. In addition, results show that the quality of perovskite films should be improved by enlarging the grain size to decrease the trap states at grain boundary. Finally, the optimal efficiency of two-terminal CH3NH3PbI2Br/CIGS tandem solar cells reaches 31.13%.