Impact of Gettering and Hydrogenation on Sub-Band-Gap Luminescence from Ring Defects in Czochralski-Grown Silicon

Abstract

Ring defects often occur in n-type Czochralski-grown silicon wafers during intermediate- to high-temperature annealing and become more recombination-active with increasing anneal durations. Such defects can significantly reduce the efficiency of solar cells. In this work, low-temperature photoluminescence (PL) spectra were measured from such ring defects, which emit a broad defect-related luminescence (DRL) peak centered at 0.9 eV. Quantitative comparisons of the DRL peak area between samples are generally not possible when using a constant laser power due to the significantly different carrier lifetimes, resulting in a different injection level and peak intensity. We show that this complication may be circumvented by varying the excitation laser power to achieve a constant band–band PL intensity from each sample, resulting in the same average injection level. The broad DRL peaks were then deconvoluted into three individual component peaks centered at 0.88, 0.93, and 1 eV. The impact of hydrogenation and phosphorus diffusion gettering steps was investigated on the individual components of the DRL peaks. Both hydrogenation and phosphorus diffusion gettering steps suppressed the broad DRL peak. However, the individual deconvoluted peaks were suppressed to different degrees. We observed that when the component peak from the deeper energy level (0.88 eV) is dominant, the ring defects can be completely passivated by hydrogenation. However, when the component peaks from the shallower energy levels (0.93 and 1 eV) dominate the DRL peak, hydrogenation is less effective for the passivation of ring defects.

Aqueous Synthesis of Ultrastable Dual-Color-Emitting Lead-Free Double-Perovskite Cs2SnI6 with a Wide Emission Span Enabled by the Size Effect

“…The blueshift of the PL peak (band gap change) and the change of the wavenumber of the corresponding Raman peak are likely attributed to the effect of the interface energy/stress between the Cs 2 SnI 6 powder and the surrounding material (aqueous solution). 26 Different materials have different interfacial and physical properties, which can introduce different stress states (stresses) in the Cs 2 SnI 6 powder and cause the change of the bandgap. 26 The interface energy/stress can also cause the split of the energy level (as indicated by the "shoulder" mode at 365 cm −1 in the Raman spectra in Figure 4b), which corresponds to the PL "shoulder" centered at 809 nm from sub-bands in the PL spectra.…”

“…26 Different materials have different interfacial and physical properties, which can introduce different stress states (stresses) in the Cs 2 SnI 6 powder and cause the change of the bandgap. 26 The interface energy/stress can also cause the split of the energy level (as indicated by the "shoulder" mode at 365 cm −1 in the Raman spectra in Figure 4b), which corresponds to the PL "shoulder" centered at 809 nm from sub-bands in the PL spectra. It should be noted that the shoulder peaks may also come from some sub-band gap defects 27−29 and the new phase 30,31 of the Cs 2 SnI 6 powder in the aqueous solution.…”

“…The interface energy/stress can also cause the split of the energy level (as indicated by the “shoulder” mode at 365 cm –1 in the Raman spectra in Figure b), which corresponds to the PL “shoulder” centered at 809 nm from sub-bands in the PL spectra. It should be noted that the shoulder peaks may also come from some sub-band gap defects − and the new phase , of the Cs 2 SnI 6 powder in the aqueous solution.…”