Compositions to facilitate room temperature growth of an oxide layer on a substrate
Disclosed is a method, process, solar cell design, and fabrication technology for high-efficiency, low-cost, crystalline silicon (Si) solar cells including but not restricted to solar grade single crystal Si (c-Si), multi-crystalline Si (mc-Si), poly-Si, and micro-Si solar cells and solar modules. The RTWCG solar cell fabrication technology creates a RTWCG SiOx thin film antireflection coating (ARC) with a graded index of refraction and a selective emitter (SE). The resulting top surface of the SiOx oxide can be textured (TO) concomitant with the growth process or through an additional mild wet chemical step.
1. A composition for wet chemical etching of a silicon substrate and substantially simultaneous growing, at substantially room temperature, of a silicon-containing oxide layer on the silicon substrate, the composition comprising:
aqueous hydrofluoric acid (HF (aq) having a concentration ranging from 10% to 50% to facilitate etching of the silicon substrate;
iodine pentoxide (I 2 O 5 ) dissolved in the aqueous hydrofluoric acid, the iodine pentoxide having a concentration ranging from 0.3 grams per liter (g/L) to 2 grams per liter (g/L) of the aqueous hydrofluoric acid, to promote an oxidation reaction at a surface of the silicon substrate and thereby facilitate growing of the silicon-containing oxide layer on the silicon substrate; and
a non-invasive additive to control a balance between a first rate of the etching of the silicon substrate and a second rate of the growing of the silicon-containing oxide layer.
2. The composition of claim 1 , wherein the non-invasive additive is selected from NH 4 F, HF, HCl, H 2 O, HNO 3 and H 2 O 2 .
3. The composition of claim 2 , wherein the non-invasive additive is HCl.
4. A composition for room temperature wet chemical growth of an oxide-based layer on, and contiguous with, a semiconductor substrate, the composition consisting essentially of:
HF, wherein the HF is aqueous hydrofluoric acid (HF (aq) having a concentration ranging from 10% to 50%;
HCl;
an iodine-containing inorganic reduction-oxidation system, wherein the inorganic reduction-oxidation system is I 2 O 5 and the I 2 O 5 is dissolved in the aqueous hydrofluoric acid and has a concentration ranging from 0.3 grams per liter (g/L) to 2 grams per liter (g/L) of the aqueous hydrofluoric acid; and
water,
wherein the composition is substantially free of silicon.