Improvement of photon collection in Cu(In,Ga)Se_2 solar cells and modules by fluorescent frequency conversion

摘要

Fluorescent photon down conversion for the improvement of the blue response of ZnO/CdS/Cu(In,Ga)Se_2 heterojunction solar cells and modules is investigated. Fluorescent dyes of the series Lumogen~® F are analyzed by optical transmission and reflection as well as by photoluminescence measurements. A spectral transfer matrix formalism is introduced that allows to predict the suitability of a luminescent dye as a down-converter for a given solar cell from its absorption/emission properties. We find that Lumogen~® F Violet 570 and Lumogen~® F Yellow 083 as well as a combination of both yields improvements for Cu(In,Ga)Se_2 solar modules. Particularly, we find that the short circuit current density of a Cu(In,Ga)Se_2 mini-module is improved by 1.5 mA cm~(-2) when applying a varnish with a combination of Lumogen~® F Violet and Yellow. About 0.5 mA cm~(-2) of this improvement is due to a reduced overall reflectance and an improvement of 1 mA cm~(-2) results from the frequency conversion by the dyes.