What you're using is more or less the official way Apple suggests to take a screenshot.
The problem is that this method takes a screenshot of your application output on screen and not of your whole screen. The status bar is in its own window and could not be taken within your application.
You should create your own status bar as an image and add it to your project or just cut the part of the screenshot you don't need.
Then, I suggest to search the forum for possible duplicate of your question, like this one: Capturing full screenshot with status bar in iOS programmatically