Almost all cell phone power modules sold in the US are dual voltage (read the fine print on the module to confirm yours is) so they will run on both 110 Volts (US) or 220 Volts (rest of the world). All you need is an adapter that physically converts a two (flat) prong US plug to three (rectangular) prongs used by receptacles in Ireland.
If you do a search on this forum you'll see numerous threads on this topic. One great suggestion is to also bring a small travel multi-outlet strip so you can plug in and charge multiple devices at the same time with one adapter. The one pictured below has 4 outlets. Some also have USB power ports.
To be safe, I bought an adapter "kit" at Bed, Bath and Beyond for about $20.00. The components will work in any country. I used it throughout Ireland (in some configuration of plugs and adapters) with a variety of electronics. Best investment I made for international travel.
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If you do a search on this forum you'll see numerous threads on this topic. One great suggestion is to also bring a small travel multi-outlet strip so you can plug in and charge multiple devices at the same time with one adapter. The one pictured below has 4 outlets. Some also have USB power ports.