How can I read large QRs in Android? I have used the Zxing app here but I cannot read large QRs with it, how can I do that? By Large, I mean that I want read a content with a lot of text (I am able to make them as large as possible by dimension but not in content).

Now I am not meaning the technical specs as given by one answer (certainly they reveal somethnig), I am looking for ways to read large-amount of content in QRs without too much lag. Is this a pipe dream, just better device or better software?
QR codes have limitations on the amount of data that can be stored within them. If you are hitting these limitations then you may need to find workarounds such as making the QR code text a hyperlink to the long text you wish to display.

For more information on the limitations of QR codes, see the "Storage" section of the Wikipedia article and its citations.

This citation in particular will be very useful to you. Look at version 40 of the standard in that table, as it has the highest capacity and will give you the absolute length limits.