RIE‐induced carrier lifetime degradation

Abstract

Reactive Ion Etching (RIE) is used in the fabrication of some types of solar cells to achieve a highly directional etch. However, cells fabricated using RIE have lower than expected efficiency, possibly caused by increased carrier recombination. Characterisation of the carrier lifetime in solar cells was conducted using the quasi steady state photoconductance (QSSPC) measurement technique. Substantial effective lifetime degradation was observed for silicon samples processed by RIE. Lifetime degradation for samples where RIE etches into silicon is found to be permanent, while for samples where RIE etches only on dielectric layers of SiO 2 grown on the wafer, the lifetime degradation is found to be reversible. The reversible degradation in RIE-processed samples is associated with radiation damage. By reducing the proportion of a wafer exposed to RIE, the degradation of the effective lifetime of RIE-etched silicon samples can be minimised, and the performance of silicon solar cells can be improved significantly.

Light trapping in pyramidally textured crystalline silicon solar cells using back‐side diffractive gratings

“…Furthermore, spatially resolved EQE measurements with rear illumination reveal a local inhomogeneity of the back‐side passivation quality. Reactive ion etching of the grating might damage the back‐surface and introduce defects thereby increasing back‐surface recombination velocities. Thus, the key challenges in experimentally achieving a performance gain by employing a back‐side grating are (i) an optimized grating geometry with high reflectance into higher orders that are subsequently trapped; (ii) low parasitic absorption in the back‐side mirror by using a thick PL and by avoiding texturing; and (iii) high back‐surface passivation quality to minimize electron–hole recombination at the grating surface and enable generated carriers to reach the contacts.…”

Improved Reflectance for Textured Mc-Silicon Solar Cells by SF6/O2 Plasma Etching

“…Such kind of etching was predominantly by chemical reaction, therefore the surface damage was much lower than ion bombardment damage of other reactive ion etching processes [14][15][16][17][18]. In order to evaluate the impact of the texturing process, the total (specular and diffuse) hemispherical reflectance and microstructure were measured after etching using a Varian Cary 500UV-VIS-NIR spectrophotometer and scanning electron microscopy (SEM) respectively.…”

Inverted Pyramidal Texturing of Silicon Through Blisters in Silicon Nitride

“…Low-average reflectance value of 6% was reported [13]. However, the usage of RIE for etching the silicon surface is reported to result in an irreversible degradation in the carrier lifetime of silicon [14].…”