Włącz and other 65,000 icons from Icons8 icon pack follow the visual guidelines of the operating systems: Windows, iOS, Android KitKat, and Material. PNG format is free up to 100x100 px. Icons are availble for download in PNG and vector (SVG, PDF, EPS, and more).
This icon looks like a switch which can be toggled by sliding left to right. The border of the switch is a rounded oval, and the button itself is a circle which slides between two positions from left to right. The icon shows the circle in the right position.