SIMS study of Na in CIGS and impurities in CdTe/CdS

Impurities can adversely affect wafer yields and solar cell performance. Secondary Ion Mass Spectrometry (SIMS) is a very effective technique to quantitatively measure the elemental impurity concentrations in CIGS and CdTe based thin film solar cells. Na in CIGS: Na is an important composition element in CIGS based solar cells. SIMS depth profiles can provide the Na concentration distribution throughout the CIGS layer. The variation of compositions in different layers in CIGS presents a challenge for SIMS to accurately quantify Na concentrations, because SIMS quantification relies on reference materials with compositions that match the compositions of the different layers. In this study, we will present SIMS results of Na in CIGS films with different compositions, and solutions that can provide accurate Na quantification (within +-15%) of CIGS samples with unknown compositions. Impurities in CdTe/CdS: SIMS quantification at the CdTe/CdS interface and thin CdS layer is difficult due to change of materials. In this study, we will present solutions for accurate quantifications in CdTe/CdS.