Chalcogenide Thin-Film Solar Cells

Solar cells based on Cu(In1-xGax)Se2 (CIGS) thin film absorbers show very high efficiencies and performance stabilities. Empa has developed a scalable deposition process for CIGS thin-film solar cells suitable for high-speed and in-line production on flexible polymer foils. The thickness of the completed solar cell including the polymer substrate is less than 25 µm.

A world record efficiency of 20.8% was recently achieved.

Main research topics include:

  • engineering of band gap, composition and interfaces of the CIGS absorber for optimum device efficiency and upscaling potential,
  • investigation of the solar cell electrical, optical properties as well as performance loss mechanisms,
  • advances with alternative environmental-friendly processes for other constituent layers,
  • development of low-bandgap absorbers for high-performance multijunction (tandem) solar cells


The development of highly efficient, stable, light weight and flexible solar cells is important for emerging markets such as building-integrated (BIPV), portable electronics, mobility as well as for aerospace applications. A spin-off of the group scales-up and commercializes solar modules based on the technology developed in the lab.

Selected publications:
  • Carron, R., Nishiwaki, S., Feurer, T., Hertwig, R., Avancini, E., Löckinger, J., Yang, Sh., Buecheler, S., Tiwari, A. N. (2019). Advanced alkali treatments for high‐efficiency Cu(In,Ga)Se2 solar cells on flexible substrates. Advanced Energy Materials, 9 (24), 1900408 (8 pp.).
  • Feurer, T., Carron, R., Torres Sevilla, G., Fu, F., Pisoni, S., Romanyuk, Y. E., Buecheler, S., Tiwari, A. N. (2019). Efficiency improvement of near‐stoichiometric CuInSe2Solar cells for application in tandem devices. Advanced Energy Materials, 9 (35), 1901428 (6 pp.).
  • Weiss, T. P., Bissig, B., Feurer, T., Carron, R., Buecheler, S., & Tiwari, A. N. (2019). Bulk and surface recombination properties in thin film semiconductors with different surface treatments from time-resolved photoluminescence measurements. Scientific Reports, 9 (1), 5385 (13 pp.).

Romain Carron

Dr. Carron Romain

Group Leader

Phone +41 58 765 47 91