Perovskite Silicon Tandem Solar Cells

© Fraunhofer ISE

Rasterelektronenmikroskop-Aufnahme einer Perowskit-Silicium-Tandemsolarzelle mit Silicium-Heterojunction-Bottom-Zelle und Perowskit-Top-Zelle mit mesoporöser, regulärer Struktur.

© Fraunhofer ISE

Sketch of a two-terminal perovskite silicon tandem solar cell with advanced optics using light trapping at the rear.

In recent years, generating electricity with silicon solar cells has become much cheaper. Most of the remaining costs scale with the cell area.  Therefore, increasing the efficiency is an effective lever to further reduce the generating costs of photovoltaic electricity. In order to overcome the theoretical efficiency limit of pure silicon photovoltaic cells, we are developing Perovskite silicon tandem solar cells.

Perovskite solar cells can use the highly energetic blue and green light much more efficiently than silicon solar cells.  On the other hand, silicon solar cells use the red and infrared light while Perovskite solar cells cannot. By combining these efficient single cells, we aim to achieve efficiencies above the so-called Auger limit of 29.4 %.

Using silicon for the bottom subcell is attractive since we can rely on an established and cost-effective production technology. The Perovskite solar cell as top cell is potentially cheap to manufacture and makes a higher efficiency possible. 

Research focus

  • Tandem solar cell architectures with high efficiency potential
  • Transparent, selective contact layers
  • Stable, environmentally friendly Perovskite absorbers with customized band gap
  • Process sequences for manufacturing efficient tandem solar cells
  • Customizing the silicon bottom cell to the requirements of the tandem configuration
  • Photon management for optimizing the quantum efficiencies and current matching
  • Optical modelling of entire tandem solar cells and modules
  • Exact characterization of cell parameters (current-voltage characteristic, quantum efficiency)
  • Spatially resolved material and cell analyses with photoluminescence, thermography, LBIC including microscopic analysis
  • Time resolved photoluminescence to determine local charge carrier lifetimes
  • Development of methods for efficiency analysis of tandem solar cells and subcells in compound solar cell


Laboratory and Facilities

  • Glove boxes for cell processing in an inert atmosphere
  • Vacuum processes like sputtering, evaporation and atomic layer deposition (ALD) to produce transparent contact layers
  • Solar cell characterization (IV-characteristic, stabilized efficiency, EQE, spatially resolved photoluminescence)
  • Material characterization (optical spectroscopy, spatially resolved steady state and transient photoluminescence, XRD, micro-LBIC, electron microscopy, lock-in thermography)
  • Clean room to fabricate high efficiency silicon bottom cells
  • Micro and nano structurization laboratories for photomanagement structures