Some flagship grade Android smartphones around the world, flaunt a so-called efficient OLED or AMOLED panel which is said to be efficient. OLED is abbreviated as ‘Organic Light Emitting Diode‘ which implies that each individual pixel present on the display panel will be producing light on its own. But this is not the case in the normal IPS grade or LTPS type LCD (Liquid Crystal Display) display panels that are being used in most of the mobiles that we use.
The LCD panels solely rely on a solid back-light which is produced at once from the whole screen. Therefore, if you use a black wallpaper on your Android smartphone, each diode on your screen will be producing minimum light and this will relatively increase the battery life of your smartphone.
If your Android smartphone sports an LCD display, other than using a black wallpaper you can also use various grades of battery savers available on your smartphone and keep the screen brightness level as low as possible. You can also decrease the screen timeout duration and turn off your data when not required. Such practices will help you to add up your battery life!