Short-circuit current density improvement of inverted polymer solar cells using PbPc to enhance photon absorption over 600 nm

We demonstrate a type of inverted polymer solar cells with the structure of indium tin oxide (ITO)/titanium dioxide (TiO2)/regioregular poly-(3-hexylthiophene; RR-P3HT): [6,6]-phenyl C60 butyric acid methyl ester (PCBM)/lead phthalocyanine (PbPc)/Molybdenum trioxide(MoO3)/Ag PbPc, which is well known as a p type material, has a strong absorption from 600–800 nm, where large numbers of photons exist in AM 1.5 radiation. It is found that the bulk heterojunction of P3HT:PCBM and the bilayer heterojunction of PCBM/PbPc existed simultaneously, and the two solar cells are parallel. The short-circuit current density with PbPc is dramatically improved compared with that without PbPc. We attribute this improvement to fabricating the tandem solar cells. The photon absorption is significantly enhanced due to introduction of PbPc. The thickness dependence of PbPc on the device performance is investigated in detail.