Vivo Y91 (Mediatek official Pictures. Vivo Y91 (Mediatek is a Smartphone of vivo. The Vivo Y91 (Mediatek) Android Smartphone. Announced Jan 2019. Features 6.22″ Display MT6762 Helio P22 Chipset 4030 MAh Battery 64 GB Storage 3 GB RAM. Vivo Y91 (Mediatek price starts.