Absorbing photonic crystals for thin film photovoltaics

TL;DR

This paper demonstrates that periodic photonic crystal patterns can significantly enhance light absorption in thin amorphous silicon layers, improving solar cell efficiency through theoretical and experimental methods.

Contribution

It introduces a novel approach of using photonic Bloch modes in patterned thin films to boost absorption, validated by simulations and large-area holographic fabrication.

Findings

Over 50% absorption enhancement in the 380-750nm spectrum

Successful large-area holographic patterning of photonic crystals

Experimental confirmation of theoretical absorption improvements

Abstract

The absorption of thin hydrogenated amorphous silicon layers can be efficiently enhanced through a controlled periodic patterning. Light is trapped through coupling with photonic Bloch modes of the periodic structures, which act as an absorbing planar photonic crystal. We theoretically demonstrate this absorption enhancement through one or two dimensional patterning, and show the experimental feasibility through large area holographic patterning. Numerical simulations show over 50% absorption enhancement over the part of the solar spectrum comprised between 380 and 750nm. It is experimentally confirmed by optical measurements performed on planar photonic crystals fabricated by laser holography and reactive ion etching.