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.