Formation of porous silicon for large-area silicon solar cells: A new method

Silicon Porosification: State of the Art

“…They have been developed to produce porous silicon layers as emitters in solar cells, since the use of electrochemical etching was found to yield low conversion efficiencies. 232,354 Vapor etching was also investigated to address the difficulty of isolating metal contacts of devices from the electrolyte solution in anodic etching. 355 Spark erosion was tested for preparing porous Si as well.…”

Porous Silicon Formation by HNO3/HF Vapor Etching

“…In contrast, no significant differences (Fig. 3) were noticed between VE-based p-and p +-type PS (Saadoun et al 1999); both p-and p +-type PS were found to be mesoporous and formed with interconnected cluster-like structures with sizes roughly ranging from 20 to 50 nm. The p +-type PS presents a more disordered morphology (Fig.…”

“…From TEM and HRTEM (Fig. 4a, b), one may notice that the clusters forming PS consist of small Si particles, having size dimensions less than 5 nm and having different crystallographic orientations and embedded in an amorphous phase (Saadoun et al 1999). (Saadoun et al 1999), (d) p + type, (e) n type, and (f) n + type…”

“…However, in all cases the HF etching time cannot exceed 10 s then preventing destructing the front contacts, particularly. In 1999 and for the first time, Saadoun et al exposed the emitter of Si solar cells to HF vapors supplied by a spray etching apparatus executing an X-Y scanning (Saadoun et al 1999). Unexpectedly, Saadoun et al discovered that when no X-Y scanning is executed, a porous silicon film (PS) forms around the sprayed area, due to the high velocity of the HF droplets striking the substrate.…”

Porous silicon‐based microtexturing of textured monocrystalline silicon solar cells

“…HNO 3 /HF mixtures were applied in wet chemical etching of silicon [2] for the removal of sawing damage as well as in various steps for silicon solar cells production. HF and HNO 3 /HF based solutions have been also used for spray etching [3] and vapor etching (VE) silicon [4], respectively. The latter techniques were found to be efficient for the production of homogeneous and reproducible porous silicon (PS) layers on the emitter of silicon solar cells, as compared to conventional etching techniques (stain etching or electrochemical etching) that found to yield low conversion efficiency due the aggressiveness of these methods.…”