@drmaddkap Presuming that such a device exists, you'd be better off with a display that includes an integrated battery.

* Screens eat up a lot of power as compared to other types of electronic components (generally, a lot of the "power budget" of a phone's battery goes to the screen).
* Physically larger and/or higher resolution screens consume comparatively more power.
* Attaching a power hungry device to a phone and powering it that way will markedly reduce how long the phone's charge lasts.