New electron donor in planar heterojunction: Optimization of the cells efficiency through the choice of the hole-extracting layer

Abstract

Due to their light weight, flexibility and semi-transparency the organic photovoltaic cells play an important role for solar conversion photovoltaic (OPV). To achieve good performances, both donor and acceptor materials in OPVs need to have good extinction coefficients, high stabilities and good film morphologies. Since the donor plays a critical role as the absorber to solar photon flux, donor materials require wide optical absorption to match the solar spectrum. In this work the couple ED/EA in planar heterojunction was Tetracyano 4,4'-bis(9Hcarbazol-9-yl) biphenyl (TCC)/fullerene (C60). Optimum results are obtained when MoO3 alone is used as Hole Transporting Layer (HTL). The J/V characteristics do not exhibit S-shaped curves up to a TCC layer thickness of 15 nm, while they did when the HTL includes CuI. Theoretical study, complementary to the experimental study, shows that in the case of S-shaped curve the cell behaves as if it was made up of 2 diodes, one of which would be opposed to the flow of the photogenerated current. In the case of MoO3 HTL, i.e; without shaped curve, the optimum thickness is 13 nm, giving an efficiency η = 2.30% with V oc = 0.9 V, J sc = 5.17 mA/cm2 and FF = 49%.