3D-printed external light trap for solar cells

Lourens Van Dijk*, Ulrich W. Paetzold, Gerhard A. Blab, Ruud E.I. Schropp, Marcel Di Vece

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review


We present a universally applicable 3D-printed external light trap for enhanced absorption in solar cells. The macroscopic external light trap is placed at the sun-facing surface of the solar cell and retro-reflects the light that would otherwise escape. The light trap consists of a reflective parabolic concentrator placed on top of a reflective cage. Upon placement of the light trap, an improvement of 15% of both the photocurrent and the power conversion efficiency in a thin-film nanocrystalline silicon (nc-Si:H) solar cell is measured. The trapped light traverses the solar cell several times within the reflective cage thereby increasing the total absorption in the cell. Consequently, the trap reduces optical losses and enhances the absorption over the entire spectrum. The components of the light trap are 3D printed and made of smoothened, silver-coated thermoplastic. In contrast to conventional light trapping methods, external light trapping leaves the material quality and the electrical properties of the solar cell unaffected. To explain the theoretical operation of the external light trap, we introduce a model that predicts the absorption enhancement in the solar cell by the external light trap. The corresponding calculated path length enhancement shows good agreement with the empirically derived value from the opto-electrical data of the solar cell. Moreover, we analyze the influence of the angle of incidence on the parasitic absorptance to obtain full understanding of the trap performance.

Original languageEnglish
Pages (from-to)623-633
Number of pages11
JournalProgress in Photovoltaics: Research and Applications
Issue number5
Publication statusPublished - 1 May 2016


  • 3D printing
  • anti-reflection
  • compound parabolic concentrator (CPC)
  • external light trapping
  • thin-film solar cells


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