If the display of your android device is turned off due to device entering into sleep state, we can wakeup android using adb shell commands with the help of input keyevent command as below.
Wakeup Android from Sleep ( Turns ON display )
$ adb shell input keyevent KEYCODE_WAKEUP
Enter Android to Sleep ( Turns OFF display )
$ adb shell input keyevent KEYCODE_SLEEP
All above two things can be achieved by toggling the sleep and wakeup modes using below command,
$ adb shell input keyevent KEYCODE_POWER