Near infrared laser CdCl2 heat treatment for CDTE solar cells

The CdCl2 heat treatment (HT) is one of the most critical steps in the fabrication of high efficiency CdTe solar cells. In this study a laser based CdCl2 treatment is presented. A high power near infrared 808 nm) diode laser was used for laser annealing (LA) CdTe cells. The effect of laser power density (LPD)and annealing time on the devices was studied using photoluminescence PL), current voltage and spectral response measurements. PL spectra exhibited a correlation between the LPD and the defect density in CdTe. CdS thinning and narrowing of the CdTe bandgap was observed with increasing LPD and longer anneal times. All solar cell parameters, open-circuit voltage (VOC), short-circuit current (JSC), and fill-factor (FF), improved as a result of the laser annealing compared to as-deposited cells. The LPD was optimized with best cell parameters obtained to-date being: VOC=800mV, JSC= 23.34 mA/cm2, and FF=71%.