Effect of net carriers at the interconnection layer in tandem organic solar cells

Tandem cell with structure of indium tin oxide (ITO)/molybdenum oxide (MoO3)/fullerene (C60)/copper phthalocyanine (CuPc)/C60/tris-8-hydroxy-quinolinato aluminum (Alq(3))/Al was fabricated to study the effect of net carriers at the interconnection layer. The open circuit voltage and short circuit current were found to be 1.15 V and 0.56 mA/cm(2), respectively. Almost the same performance (1.05 V, 0.58 mA/cm(2)) of tandem cell with additional recombination layer (ITO/MoO3/C60/Alq(3)/Al/Ag/MoO3/CuPc/C60/Alq(3)/Al) demonstrates that the carrier balance is more crucial than carrier recombination. The net holes at the interconnection layer caused by more carrier generation from the back cell on one hand would enhance the recombination with electrons from the front cell and on the other hand would quench the excitons produced in CuPc of the back cell.