Photonic crystals for enhanced absorption in thin film solar materials

Photonic crystals are designed as back reflectors for thin film amorphous silicon cells. Optimum absorption of red and near infrared photons are found using rigorous scattering matrix simulation. Using photo-lithography and reactive ion etching these photonic-plamsonic crystal substrates have been fabricated and solar cells have been grown on top of them. Experimental solar devices demonstrate 7-8{\%} improved absorption with superior harvesting of red and near infrared photons. Comparison with random roughened back reflectors and plasmonic schemes using metallic nanoparticles will be made.