Abstract
The efficiency of Cu(InGa)Se2 (CIGS) solar cells with high Ga content fabricated by the three-stage method is lower than that with low Ga content in spite of a better matching solar spectrum. Secondary ion mass spectrometry (SIMS) measurement revealed that the band profile of CIGS films with high Ga content had a deep notch around 0.5 µm from the CdS/CIGS interface. In order to decrease the notch depth of the CIGS with high Ga content, the five-stage method was employed instead of the conventional three-stage method. As a result, we successfully obtained the efficiency of 14.9% using the CIGS absorber with an average band gap of 1.40 eV prepared by the five-stage method. Theoretical simulation revealed the effects of the notch location and depth on solar cell performance characteristics.