A Robust Inter-Connecting Layer for Achieving High Performance Tandem Polymer Solar Cells

摘要

Recently, polymer solar cells (PSCs) have attracted much atten tion primarily due to their potential for fabricating low-cost and large-area flexible solar cells.[1-3] Smart chemistry can design conjugated polymeric structures for PSCs with enhanced open circuit voltage (Voc) and short-circuit current density (Jsc). This has resulted in significant efficiency enhancements in recent years. Nonetheless, most of the materials designed today always suffer from the inherent disadvantage of not having a broad absorption range, which limits the utilization of the full solar spectrum.[4,5] A possible solution is to stack multiple photo active layers wherein the photoactive layers have complemen tary absorption. Recently, multiple-junction tandem PSCs with various configuration have been demonstrated, in which two polymerfullerene bulk heterojunctions (BHJs) are connected in series or parallel to fulfill this goal.[6-8] These configurations enable reduction of potential loss during photon-to-electron conversion process, and add-up of electrical potential or photo current of the individual BHJs, while the combination of poly mers with complimentary bandgaps broadens absorption band ranging 300 nm up to 900 nm, covering a larger portion of the solar spectrum. Recently, a 7.7% PCE from small organic molecule-based tandem solar cells has been achieved.[9] it strongly indicats that tandem structure is one of the promising approaches to break though 10% theoretical limit for single junction-based polymer solar cells.[10]