Effects of Alkali Elements on Copper Indium Gallium Aluminum Selenide Flexible Solar Cells Fabricated on Polyimide Substrates.

Polycrystalline Cu(InGaAl)Se (CIGAS) thin films were prepared on polyimide (PI) foils by depositing aluminum (Al) and CIGS precursor layers. Three ceramic CIGS quaternary targets with different sodium (Na) contents were used for investigating the influences of alkali doping at an annealing temperature of 500 °C. The Al concentration was enriched at the front interfaces of absorber films with different Na doping amounts after annealing.