A new ladder-type benzodi(cyclopentadithiophene)-based donor–acceptor polymer and a modified hole-collecting PEDOT:PSS layer to achieve tandem solar cells with an open-circuit voltage of 1.62 V

We have developed a new ladder-type conjugated polymer PBDCPDT–FBT and a robust interconnecting layer (ICL) integrating a hole-collecting m-PEDOT:PSS layer with an electron-collecting ZnO layer. The inverted device using PBDCPDT–FBT exhibited a high power conversion efficiency (PCE) of 5.76% with a Voc of 0.81 V, a Jsc of 12.82 mA cm−2, and a FF of 55.5%. The inverted tandem device incorporating the PBDCPDT–FBT and ICL achieves a Voc of 1.62 V leading to a PCE of 7.08%.