We present a single-friction-surface triboelectric generator (STEG). The STEG is transparent and flexible, making possible the use of triboelectric generators in an extended range of applications. This device is fabricated in a simple and very low-cost way. When tapped with a finger, the STEG with micro-patterned PDMS surface achieved an open-circuit voltage over 130 V with a short-circuit current density of about 1 μA cm⁻². A STEG with a flat PET surface is employed as a transparent cover on the screen of a smartphone to generate electric energy from the control motion of the users. The STEG can directly power 3 LEDs when the phone screen is tapped during normal use. In addition, based on the STEG, we have developed a self-powered visualized touch sensor with 4 STEGs serving as the touch pads. The STEG shows promise for applications in systems such as self-powered touch panels and artificial skins.