Hello.
I'd done some research activity with display panel manufacturer and was involved with laser-based silicon crystallization in which amorphous silicon is converted to poly-silicon (poly-crystalline silicon). It is known that poly-silicon has 100 times higher mobility than amorphous so it is preferred. in this sense, I guess mono-crystalline silicon is the best.
My question is this: why display panel manufacturer is now using poly-silicon instead of mono-crystalline silicon? Making mono-crystalline requires huge cost?
Large area displays are based on LCD pixel elements or Led pixel elements. These elements are scanned by addressing through FETs acting as switches. Such switching transistor arrays are produced by thin film technology on a flexible substrates. So, such devices must be fabricated using low temperature processing. It is so the most common transistor used with the displays is the amorphous Silicon METAL INSULATOR FIELD EFFECT TRANSISTOR which is hydrogenated to enhance its electrical performance. It is the production compatibility that imposes the use of thin film a-Si transistors in LCD and LED displays.
Single crystalline silicon needs very elaborated methods to produce including relatively high temperature processing which may be not appropriate in large area displays. Yes the use of the single crystal silicon can improve much the performance of the transistors. But the processing must matches that of the other elements of the display.
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wish you success
From the other side:AFAIK, the largest monocrystalline wafers currently are round and 12" diameter. This is way smaller than what's required for displays. On the other hand, the production of monocrystalline wafers is rather expensive.
Regarding consumer products, nearly everything is about cost. Thus the lowest-cost technology is used that still fulfills the requirements: wherever feasible, you will find amorphous Si. Where this is not sufficient, you'll fild poly-Si. And only where absolutely required, monocrystalline wafers are used.
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