Why can't I get the $sceProvider?

I'm trying to create a filter using $sceProvider to unescape the HTML tags.

This is how my code looks like:

myApp.filter('unescapeHtml', function($sce) {
return function(item) {
    return $sce.trustAsHtml(item);
};

But when I use this filter in my code, this error occurs.

I searched online about this seems no working solution for me.

I did have this work in another page of my application, the only difference is that the working one is being injected into a controller, like this:

function myController($scope, $http, $sce) {

Did I miss something? I totally have no idea what's going on here, any help will be grateful.