Thermal History Index as a bulk quality indicator for Czochralski solar wafers

- A new technique is presented to estimate the wafer thermal history.
- This technique is accessible to both wafer and cell manufacturers.
- A novel bulk quality indicator, the Thermal History Index, is presented.
- The combined use of this indicator and oxygen data helps detect low quality wafers.

A significant fraction of Czochralski (Cz) Silicon (Si) wafers suffer from oxygen-related bulk quality issues. The detection of such wafers in the as-cut state during incoming inspection has become a topic of attention as higher efficiency solar cell structures are developing. However such detection - for instance using photoluminescence images - has not yet proven successful due to a high risk of detection errors Shih et al. (2015) [1]. In this work, we tentatively introduce a material quality indicator referred to as “Thermal History Index” (THI) and investigate its ability, in conjunction with the interstitial oxygen concentration ([Oi]), to allow a better identification of low bulk quality wafers.