안녕하세요
매니페스트에 추가하신거죠?
<!-- 화면깨우기 권한 -->
<uses-permission android:name="android.permission.WAKE_LOCK" />
이렇게 해보세요~
if (wakeLock != null) {
    return;
}
PowerManager pm = (PowerManager) getApplication().getSystemService(Context.POWER_SERVICE);
wakeLock = pm.newWakeLock(
        PowerManager.SCREEN_BRIGHT_WAKE_LOCK |
                PowerManager.ACQUIRE_CAUSES_WAKEUP |
                PowerManager.ON_AFTER_RELEASE, "");
wakeLock.acquire();
if (wakeLock != null) {
    wakeLock.release();
    wakeLock = null;
}