Can I export to Android but at a different resolution?

Hi...

My game, a space-shooter has a few sprites in scene at times and its the performance I'm trying to improve upon on a mobile device, you see on a PC/Mac etc it's a breeze, but my Android version has some spiky moments in terms of slow-down... I have a Samsung Note-4 device and it works fine on this with said lag at times but I'm wondering if the high resolution of my phones display is causing the unity to work overtime, so is it possible to reduce the resolution or force it on export to something else on a phone/android device? please advise and thanks