Hello Rikka and welcome to our forum!
We're happy to hear that you'll be visiting Dublin soon!
As you can read on the gov.ie website,
only Rapid Antigen Tests which are listed on the common EU Rapid Antigen Test list will be accepted, and it must be carried out by a health professional or skilled testing personnel.
When you do an antigen test, you'll get a certification with a QR code to show when requested by the airline or by the authorities, so yes, the document must contain a QR code to be valid.
You can find more information about the Digital COVID Certificate and how to get it on this page.
I hope this helps,
Have a great day and enjoy your stay in Dublin!