Berlin 2015 – scientific programme

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DS: Fachverband Dünne Schichten

DS 14: Plasmonics and nanooptics: Structure, fabrication and characterization (joint session with O)

DS 14.2: Talk

Tuesday, March 17, 2015, 10:45–11:00, MA 043

Light trapping and enhanced absorption in femtosecond-laser materials processed amorphous thin-film silicon — Dominik Differt¹, •Walter Pfeiffer¹, Babak Soleymanzadeh¹, and Helmut Stiebig^1,2 — ¹Fakultät für Physik, Universität Bielefeld, Universitätsstr. 25, 33615 Bielefeld, Germany — ²Institut für Innovationstransfer an der Universität Bielefeld, Universitätsstr. 25, 33615 Bielefeld, Germany

Efficient thin-film solar cells balance the reduced absorption in thin absorber layers by means of various photon management strategies that often involve nanotextured interfaces. We report broadband absorption enhancement in femtosecond (fs) laser materials processed thin amorphous silicon. The absorption of a single amplified fs laser pulse (30 fs, 795 nm, 75 mJ cm⁻²) creates a thin nanotextured micro-crystalline surface layer. Coherent scattered light micro-spectroscopy in combination with spectral interferometry reveals that incident radiation is trapped for about 100 fs in localized photonic modes in the laser processed area. This trapping explains the enhanced absorption and the observed local Raman yield enhancement. The lateral correlation length of the light trapping modes indicates very efficient light scattering in the processed layer that leads to strong localization of light in the absorber layer. Consequently, fs materials processing offers an interesting pathway towards advanced photon management in amorphous silicon based thin-film solar cells.