Reliability and performance of organic down-shifting films for CdS/CdTe solar cells

An organic luminescent film is attached to CdS/CdTe solar cells to improve device performance. The luminescent film serves to absorb high energy photons that would normally be unharvested due to parasitic window layer absorption and re-emits photons at lower energies, better matched to the quantum efficiency peak of the solar cell. Efficiency improvements of up to 8.5% were obtained after optimizing dye concentration and film thickness in the luminescent layer. Long time stability tests show that the organic dye is stable for at least 5000 hours under 1 sun illumination provided that the dye is encapsulated in an oxygen and water free environment.