Voltage-Induced Transients in Methylammonium Lead Triiodide Probed by Dynamic Photoluminescence Spectroscopy

In this work, we use time-resolved photoluminescence (PL) spectroscopy, microscopy, and current measurements to characterize the slow transient responses of methylammonium lead triiodide (MAPbI₃) on a lateral interdigitated electrode device. By systematically varying the applied bias magnitude and electrode polarity, we observed distinct reversible and irreversible PL transient responses in the form of spectrally and spatially resolved PL quenching occurring over a range of 0.5–100 s. When the simultaneous current and the PL measurements were correlated, the reversible responses, present under all electric fields, were attributed to charge trapping, whereas the irreversible response, occurring above a nominal electric field between 1 and 5 kV cm^–1, was attributed to ion migration. Thus, these results indicate that the slow transient response, and therefore hysteretic behavior, in MAPbI₃ devices is a complex response with contributions from both charge trapping and ion migration

Voltage-Induced Transients in Methylammonium Lead Triiodide Probed by Dynamic Photoluminescence Spectroscopy

In this work, we use time-resolved photoluminescence (PL) spectroscopy, microscopy, and current measurements to characterize the slow transient responses of methylammonium lead triiodide (MAPbI₃) on a lateral interdigitated electrode device. By systematically varying the applied bias magnitude and electrode polarity, we observed distinct reversible and irreversible PL transient responses in the form of spectrally and spatially resolved PL quenching occurring over a range of 0.5–100 s. When the simultaneous current and the PL measurements were correlated, the reversible responses, present under all electric fields, were attributed to charge trapping, whereas the irreversible response, occurring above a nominal electric field between 1 and 5 kV cm^–1, was attributed to ion migration. Thus, these results indicate that the slow transient response, and therefore hysteretic behavior, in MAPbI₃ devices is a complex response with contributions from both charge trapping and ion migration

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%