texturing of silicon preferred mostly TMAH because of its CMOS compatibity whereever being low cost KOH and NAOH is not preferred because of its heavy mobile ion contamination. is in what sense CMOS compatibility effect solar cell performance???
Dear Arti,
welcome,
Silicon solar cells have their fabrication processes and each process has specific fabrication steps starting with surface texturing, doping , metallization and antireflective coating. Also the CMOS has its processes with a specific process flow containing its fabrication steps. The fabrication steps are designed to produce the required device structure while avoiding any side effects from contamination with unwanted impurities or heat treatments that can produce crystallographic defects.
The K or Na ions may have negligible effects on the bipolar devices such as the pn junction solar cells. THESE ions have appreciable effects on the MOS devices as they can wander in the oxide at the effect of the electric field in the oxide and cause instability in the device in the threshold voltage of the device.
By searching in the web you can get more information about the effect of sodium or Kalium ions on the MOS capacitors and MOS transistors.
Best wishes
Dear Abdelhalim,
Thanks for your response. I can understand the heavy mobile ions effect in case of cmos devices but as we go on si solar cell where people are preferring TMAH as an etchant (to create micro structures on si surface and thus reduce reflectance to increase solar cell efficiency), bcz of its cmos compatibility instead of KOH and NaoH. So here i am confuse that how a cmos incompatible solvent can effect the solar cell performance?
Dear Arti,
I do not think that the cause of not using KOH or NaOH is that they are harming the solar cell device performance. Their residual can be eliminated with acid etching of very small layers and then washing with a plenty of deionised water. May be the major cause for using TMAH is its better selective etch performance from the point of view speed of etching and the superior etch structures such as resulting in pyramids with very controlled dimensions.
Best wishes
Dear Abdelhalim ,
TMAH is more selective compare to KOH and NaOH but once you are texturing Si there is no role of selectivity. it ruled when you are making patterns. Here high etch rate etchant should prefer more and in compare to TMAH , KOH and NaOH had more etch rate. but apart of this a complete literature survey tells me that TMAH is cmos compatible thats why highly being used in solar cell texturing.
I am not able to understand that how cmos incompatible solvent affect solar cell performance.
Dear Arti,
Thank you for the paper.
The effect of using NaOH as selective etching can appear when the silicon surface of the solar cell is passivated by a layer of SiO2. This passivation layer of SiO2 grown after surface structuring with NaOH can be contaminated bu Na+ ions which are assumed to affect the solar cell operation like what happening in the MOS devices as i hinted in my first post. What exactly this effect they did not speak from it. But i would expect that it will affect some what the electric isolation capability.
Best wishes
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