Polymer solar cells (PSCs) with bulk heterojunction structure (BHJ) have attracted extensive studies due to the superiority of synthetic variability, lightweight, mechanically flexible, and inexpensive roll to roll fabrication process.1-4 As well known, open-circuit voltages (VOC) is dependent on the offset betw, een the highest occupied molecular orbital (HOMO) level of the donor polymers and the lowest unoccupied molecular orbital (LUMO) level of the fullcrene acccptor, which is critical importance for high power conversion efficiency (PCE).