Future of raman in PV development

Abstract

We introduce and demonstrate two innovative macroRaman mapping modes for advanced microstructural and mechanical characterization of photovoltaic (PV) materials. The macro-and micro-Raman results presented in this work are obtained on multicrystalline silicon (mc-Si) thin films on glass for solar cells. We show that detailed information can be extracted from the same first-order Raman spectra of solar silicon. This enables us to understand the interaction between stresses, defects, doping/impurities, and microstructure at identical positions as well as at different length scales. The fast and largescale imaging Raman instrument allows us to evaluate statistically the materials properties and to see clearly the differences originating from different preparation conditions/processing. Based on these results, we believe that the Raman technique will become increasingly important in the PV community not only for fundamental studies but also for optimization and in-line quality check in a PV factory.

Vapour-Phase and Solid-Phase Epitaxy of Silicon on Solid-Phase Crystallised Seed Layers for Solar Cells Application

“…It is well known that the broadening of the FWHM of the Raman peak occurs due to a decrease in the phonon lifetimes which is mainly a result of defects acting as anharmonic perturbations. Therefore, Raman peak FWHM can be used to qualitatively estimate defect densities [24]. FWHM of the Raman peak is averaged over nine different positions taken over the area of 25 × 25 m 2 .…”

From Micro– to Macro–Raman Spectroscopy: Solar Silicon for a Case Study

“…Thus, we attribute the stress concentrations in Figure 4(b) to particular combinations of (1) defect configurations/structures, which do not necessary result in higher FWHM values and (2) thermally induced residual stresses. The stress map is corrected for the compressive contributions produced by the Fano effect and by the addition of boron by means of the lattice parameter using Vergard's law [7]. The presence of different types of defects and their nonuniform distribution inside the laser crystallized seed layer are supported by transmission electron microscopy (TEM) investigations shown in Figure 4(g).…”

“…The two new DuoScan TM (hardware) and SWIFT TM (software) Raman scanning modules developed by HORIBA Jobin Yvon provide significant reduction by orders of magnitude of the measurement times by means of large area probing beam (macro-beam) and high speed detector-stage coordination, respectively. Even faster Raman imaging is possible by combing these two technologies [7].…”

“…The unique characterization power of the Raman technique consists in the detailed mechanical and microstructural information that can be extracted from the silicon Raman peak: (1) the peak position map -the distribution, amount and sign of internal stresses, (2) the peak full-with at half maximum (FWHM) map -the distribution and qualitative comparison of defect densities, (3) the peak asymmetry map -the distribution and amount of doping, and (4) the peak intensity map -the grain orientation and the grain boundary pattern [7,10,11].…”

“…In the field of semiconductors, Raman spectroscopy has shown to be a powerful analytic tool for investigating mechanical stress, crystallographic orientation, doping, composition, phase, and crystallinity of semiconductor materials in bulk, thin film and device form [4][5][6][7]. In particular, the use of Raman spectroscopy to study solar silicon materials in form of thin films on glass, wafers, and ribbons, which are then processed to solar cells used as a clean and sustainable energy source has gained new momentum in the context of climate change and energy security.…”