Graphene oxide-based carbon interconnecting layer for polymer tandem solar cells

Tandem polymer solar cells (PSCs), consisting of more than one (normally two) subcells connected by a charge recombination layer (i.e., interconnecting layer), hold great promise for enhancing the performance of PSCs. For an ideal tandem solar cell, the open circuit voltage (V_oc) equals to the sum of those of the subcells while keeping the short circuit current the same as the lower one, leading to an increased overall power conversion efficiency. The interconnecting layer plays an important role in regulating the tandem device performance. Here, we report that graphene oxide (GO)/GO-Cs (cesium neutralized GO) bilayer modified with ultrathin Al and MoO₃ can act as an efficient interconnecting layer in tandem PSCs to achieve a significantly increased V_oc, reaching almost 100% of the sum of the subcell V _ocs under standard AM 1.5 conditions.