The impact of luminescent down shifting on the performance of CdTe photovoltaics: impact of the module vintage

Luminescent down-shifting (LDS) performance is presented for different production-line cadmium telluride (CdTe) mini-modules manufactured in 2009 (CX1) and 2012 (CX3). The 10 cm x 10 cm mini-modules were laminated with LDS layers that consist of luminescent organic dye-doped ethylene vinyl acetate (EVA) and a fluorinated ethylene propylene (FEP) cover sheet. The external quantum efficiency of the devices was measured before and after the encapsulation. All LDS layers improved the short-circuit current. Lumogen Yellow 083 (Y083) and 170 (Y170) dyes showed the greatest relative improvement in the short-circuit current for the CX1 devices (9.6% and 9.7%, respectively), while Lumogen Yellow 083 showed the largest improvement for the CX3 (5.3%). The different vintages of modules also enabled an investigation of how the enhancement possible with LDS relates to other technological efficiency improvements for CdTe cells and indicates the level of future improvements possible. Finally, initial results of the same EVA-FEP LDS layers that contain the V570, Y083, and mixture of the two dyes are also presented for full-size (120 cm x 60 cm) CX3 production line modules (2012). The full-size module results indicate that scale up of the method is feasible with the Y083 layer, which improves short-circuit current by 4.3%.