Tandem structured polymer solar cells(PSCs)show great potential to make further improvement in device performance,1 mainly due to the enhanced light trapping and rationalized balance of thermalization loss and transmission loss compared with the single junction device.2 To achieve highly efficient tandem PSCs,it is very critical to have an optimal interconnecting layer(ICL)3 that can serve as an efficient recombination or collection site for charges extracted from sub-cells in series and parallel connection,respectively.