摘要
A comprehensive study of high efficiency In（0.46）Ga（0.54）N/Si tandem solar cell is presented.A tunnel junction（TJ） was needed to interconnect the top and bottom sub-cells.Two TJ designs,integrated within this tandem：GaAs（n^＋）/GaAs（p^＋） and In（0.5）Ga（0.5）N（n^＋）/Si（p^＋） were considered.Simulations of GaAs（n^＋）/GaAs（p^＋）and In（0.5）Ga（0.5）N（n^＋）/Si（p^＋） TJ I-V characteristics were studied for integration into the proposed tandem solar cell.A comparison of the simulated solar cell I-V characteristics under 1 sun AM1.5 spectrum was discussed in terms of short circuit current density（J（SC））,open circuit voltage（V（OC））,fill factor（FF） and efficiency（η） for both tunnel junction designs.Using GaAs（n^＋）/GaAs（p^＋） tunnel junction,the obtained values of J（SC） = 21.74 mA/cm-2,V（OC）= 1,81 V,FF = 0.87 and η=34.28%,whereas the solar cell with the In（0.5）Ga（0.5）N/Si tunnel junction reported values of J（SC）= 21.92 mA/cm-2,V（OC）= 1.81 V,FF = 0.88 and η= 35.01%.The results found that required thicknesses for GaAs（n^＋）/GaAs（p^＋） and In（0.5）Ga（0.5）N（n^＋）/Si（p^＋） tunnel junctions are around 20 nm,the total thickness of the top InGaN can be very small due to its high optical absorption coefficient and the use of a relatively thick bottom cell is necessary to increase the conversion efficiency.
A comprehensive study of high efficiency In（0.46）Ga（0.54）N/Si tandem solar cell is presented.A tunnel junction（TJ） was needed to interconnect the top and bottom sub-cells.Two TJ designs,integrated within this tandem：GaAs（n^＋）/GaAs（p^＋） and In（0.5）Ga（0.5）N（n^＋）/Si（p^＋） were considered.Simulations of GaAs（n^＋）/GaAs（p^＋）and In（0.5）Ga（0.5）N（n^＋）/Si（p^＋） TJ I-V characteristics were studied for integration into the proposed tandem solar cell.A comparison of the simulated solar cell I-V characteristics under 1 sun AM1.5 spectrum was discussed in terms of short circuit current density（J（SC））,open circuit voltage（V（OC））,fill factor（FF） and efficiency（η） for both tunnel junction designs.Using GaAs（n^＋）/GaAs（p^＋） tunnel junction,the obtained values of J（SC） = 21.74 mA/cm-2,V（OC）= 1,81 V,FF = 0.87 and η=34.28%,whereas the solar cell with the In（0.5）Ga（0.5）N/Si tunnel junction reported values of J（SC）= 21.92 mA/cm-2,V（OC）= 1.81 V,FF = 0.88 and η= 35.01%.The results found that required thicknesses for GaAs（n^＋）/GaAs（p^＋） and In（0.5）Ga（0.5）N（n^＋）/Si（p^＋） tunnel junctions are around 20 nm,the total thickness of the top InGaN can be very small due to its high optical absorption coefficient and the use of a relatively thick bottom cell is necessary to increase the conversion efficiency.
