@article{KegelmannWolffAwinoetal.2017,
  author    = {Kegelmann, Lukas and Wolff, Christian Michael and Awino, Celline and Lang, Felix and Unger, Eva L. and Korte, Lars and Dittrich, Thomas and Neher, Dieter and Rech, Bernd and Albrecht, Steve},
  title     = {It Takes Two to Tango-Double-Layer Selective Contacts in Perovskite Solar Cells for Improved Device Performance and Reduced Hysteresis},
  series = {ACS applied materials \& interfaces},
  volume    = {9},
  journal   = {ACS applied materials \& interfaces},
  publisher = {American Chemical Society},
  address   = {Washington},
  issn      = {1944-8244},
  doi       = {10.1021/acsami.7b00900},
  pages     = {17246 -- 17256},
  year      = {2017},
  abstract  = {Solar cells made from inorganic organic perovskites have gradually approached market requirements as their efficiency and stability have improved tremendously in recent years. Planar low-temperature processed perovskite solar cells are advantageous for possible large-scale production but are more prone to exhibiting photocurrent hysteresis, especially in the regular n-i-p structure. Here, a systematic characterization of different electron selective contacts with a variety of chemical and electrical properties in planar n-i-p devices processed below 180 degrees C is presented. The inorganic metal oxides TiO2 and SnO2, the organic fullerene derivatives C-60, PCBM, and ICMA, as well as double-layers with a metal oxide/PCBM structure are used as electron transport materials (ETMs). Perovskite layers deposited atop, the different ETMs with the herein applied fabrication method show a similar morphology according to scanning electron microscopy. Further, surface photovoltage spectroscopy measurements indicate comparable perovskite absorber qualities on all ETMs, except TiO2, which shows a more prominent influence of defect states. Transient photoluminescence studies together with current voltage scans over a broad range of scan speeds reveal faster charge extraction, less pronounced hysteresis effects, and higher efficiencies for devices with fullerene compared to those with metal oxide ETMs. Beyond this, only double-layer ETM structures substantially diminish hysteresis effects for all performed scan speeds and strongly enhance the power conversion efficiency up to a champion stabilized value of 18.0\%. The results indicate reduced recombination losses for a double-layer TiO2/PCBM contact design: First, a reduction of shunt paths through the fullerene to the ITO layer. Second, an improved hole blocking by the wide band gap metal oxide. Third, decreased transport losses due to an energetically more favorable contact, as implied by photoelectron spectroscopy measurements. The herein demonstrated improvements of multilayer selective contacts may serve as a general design guideline for perovskite solar cells.},
  language  = {en}
}
@article{JoštAlbrechtKegelmannetal.2017,
  author    = {Jošt, Marko and Albrecht, Steve and Kegelmann, Lukas and Wolff, Christian Michael and Lang, Felix and Lipovšek, Benjamin and Krč, Janez and Korte, Lars and Neher, Dieter and Rech, Bernd and Topič, Marko},
  title     = {Efficient light management by textured nanoimprinted layers for perovskite solar cells},
  series = {ACS photonics},
  volume    = {4},
  journal   = {ACS photonics},
  publisher = {American Chemical Society},
  address   = {Washington},
  issn      = {2330-4022},
  doi       = {10.1021/acsphotonics.7b00138},
  pages     = {1232 -- 1239},
  year      = {2017},
  abstract  = {Inorganic-organic perovskites like methylammonium-lead-iodide have proven to be an effective class of 17 materials for fabricating efficient solar cells. To improve their performance, light management techniques using textured surfaces, similar to those used in established solar cell technologies, should be considered. Here, we apply a light management foil created by UV nanoimprint lithography on the glass side of an inverted (p-i-n) perovskite solar cell with 16.3\% efficiency. The obtained 1 mA cm(-2) increase in the short-circuit current density translates to a relative improvement in cell performance of 5\%, which results in a power conversion efficiency of 17.1\%. Optical 3D simulations based on experimentally obtained parameters were used to support the experimental findings. A good match between the simulated and experimental data was obtained, validating the model. Optical simulations reveal that the main improvement in device performance is due to a reduction in total reflection and that relative improvement in the short-circuit current density of up to 10\% is possible for large-area devices. Therefore, our results present the potential of light management foils for improving the device performance of perovskite solar cells and pave the way for further use of optical simulations in the field of perovskite solar cells.},
  language  = {en}
}