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Reducing Optical Losses

A major technological challenge for tandem solar cells is to minimize optical losses and direct equal portions of light into both absorbers to achieve so-called “current-matching”. This requires the development of low-absorption charge transport layers (see also Development of New Contact Materials), an optimization of layer thicknesses and the deployment of neat light management strategies. In this field, we collaborate closely with the Optics for Solar Energy group of Christiane Becker.



  • In a simulation study, we compared regular and inverted device architectures and calculated their optimum performance by adjusting layer thicknesses. The optical performance of perovskite solar cells can be further improved by the implementation of textured interfaces such as nanotextures or pyramidal microtextures or the use of add-on foils.
  • In a combined experimental and simulation study, we investigated the effect of textured interfaces in tandem solar cells and found that such structures are important to maximize the optical yield of tandem solar cells [1]. By applying a light management foil to tandem solar cells, we achieved a 1.2 mA/cm² increase in photogenerated current density translating to an improvement of the device performance by 2%.
  • In the context of textured tandem solar cells, we also investigated the growth behavior of co-evaporated perovskite layers on random pyramidal microtextures and achieved a significant reduction in reflection losses.  
  • We implemented nanotextures into perovskite single-junction solar cells to enhance the light trapping [2]. These nanotextures strongly reduced reflection losses and increased the short-circuit current by 1 mA/cm². Remarkably, at the same time the optoelectronic properties of the perovskite were preserved, and a 1%abs efficiency increase was achieved.

Key Publications:

  1. Jošt, M.; Köhnen, E.; Morales-Vilches, A.B.; Lipovšek, B.; Jäger, K.; Macco, B.; Al-Ashouri, A.; Krc, J.; Korte, L.; Rech, B.; Schlatmann, R.; Topic, M.; Stannowski, B.; Albrecht, S.: Textured interfaces in monolithic perovskite/silicon tandem solar cells: advanced light management for improved efficiency and energy yield. Energy & Environmental Science 11 (2018), p. 3511-3523
    Open Access Version
  2. Tockhorn, P.; Sutter, J.; Colom, R.; Kegelmann, L.; Al-Ashouri, A.; Roß, M.; Jäger, K.; Unold, T.; Burger, S.; Albrecht, S.; Becker, C.: Improved Quantum Efficiency by Advanced Light Management in Nanotextured Solution-Processed Perovskite Solar Cells. ACS Photonics 7 (2020), p. 2589–2600
    Open Access Version (available 01.08.2021)