Append a div to the player when player goes fullscreen

I want to append a div to the player when the player goes fullscreen such that the player alongwith the div is visible on fullscreen. I tried the following:`var iframe = player.getIframe();
iframe.append('

');
var requestFullScreen = iframe.requestFullscreen || iframe.mozRequestFullscreen || iframe.webkitRequestFullscreen;
if (requestFullScreen) {
requestFullScreen.apply(iframe)
}`
but nothing happens.
Thanks in advance for any help