@article{AlbrechtGrootoonkNeubertetal.2014,
  author    = {Albrecht, Steve and Grootoonk, Bjorn and Neubert, Sebastian and Roland, Steffen and Wordenweber, Jan and Meier, Matthias and Schlatmann, Rutger and Gordijn, Aad and Neher, Dieter},
  title     = {Efficient hybrid inorganic/organic tandem solar cells with tailored recombination contacts},
  series = {Solar energy materials \& solar cells : an international journal devoted to photovoltaic, photothermal, and photochemical solar energy conversion},
  volume    = {127},
  journal   = {Solar energy materials \& solar cells : an international journal devoted to photovoltaic, photothermal, and photochemical solar energy conversion},
  publisher = {Elsevier},
  address   = {Amsterdam},
  issn      = {0927-0248},
  doi       = {10.1016/j.solmat.2014.04.020},
  pages     = {157 -- 162},
  year      = {2014},
  abstract  = {In this work, the authors present a 7.5\% efficient hybrid tandem solar cell with the bottom cell made of amorphous silicon and a Si-PCPDTBT:PC70BM bulk heterojunction top cell. Loss-free recombination contacts were realized by combing Al-doped ZnO with either the conducting polymer composite PEDOT:PSS or with a bilayer of ultrathin Al and MoO3. Optimization of these contacts results in tandem cells with high fill factors of 70\% and an open circuit voltage close to the sum of those of the sub-cells. This is the best efficiency reported for this type of hybrid tandem cell so far. Optical and electrical device modeling suggests that the efficiency can be increased to similar to 12\% on combining a donor polymer with suitable absorption onset with PCBM. We also describe proof-of-principle studies employing light trapping in hybrid tandem solar cells, suggesting that this device architecture has the potential to achieve efficiencies well above 12\%. (C) 2014 Elsevier B.V. All rights reserved.},
  language  = {en}
}
@article{AlbrechtSchaeferLangeetal.2012,
  author    = {Albrecht, Steve and Schaefer, Sebastian and Lange, Ilja and Yilmaz, Seyfullah and Dumsch, Ines and Allard, Sybille and Scherf, Ullrich and Hertwig, Andreas and Neher, Dieter},
  title     = {Light management in PCPDTBT:PC70BM solar cells: A comparison of standard and inverted device structures},
  series = {Organic electronics : physics, materials and applications},
  volume    = {13},
  journal   = {Organic electronics : physics, materials and applications},
  number    = {4},
  publisher = {Elsevier},
  address   = {Amsterdam},
  issn      = {1566-1199},
  doi       = {10.1016/j.orgel.2011.12.019},
  pages     = {615 -- 622},
  year      = {2012},
  abstract  = {We compare standard and inverted bulk heterojunction solar cells composed of PCPDTBT:PC70BM blends. Inverted devices comprising 100 nm thick active layers exhibited short circuit currents of 15 mA/cm(2), 10\% larger than in corresponding standard devices. Modeling of the optical field distribution in the different device stacks proved that this enhancement originates from an increased absorption of incident light in the active layer. Internal quantum efficiencies (IQEs) were obtained from the direct comparison of experimentally derived and modeled currents for different layer thicknesses, yielding IQEs of similar to 70\% for a layer thickness of 100 nm. Simulations predict a significant increase of the light harvesting efficiency upon increasing the layer thickness to 270 nm. However, a continuous deterioration of the photovoltaic properties with layer thickness was measured for both device architectures, attributed to incomplete charge extraction. On the other hand, our optical modeling suggests that inverted devices based on PCPDTBT should be able to deliver high power conversion efficiencies (PCEs) of more than 7\% provided that recombination losses can be reduced.},
  language  = {en}
}