How do i mark html TRUE in l()
Here is a way to do this:

$create_icon_path = 'my_icon.png'; //my icon path
$create_icon = '&lt;img height=15 src = "/' . $create_icon_path . '"&gt;';  
$create_earlywarning_url = Url::fromUserInput('/node/5');  
$link_render_array = array(
  '#title' =&gt; array(
    '#markup' =&gt; $create_icon
  ),
  '#type' =&gt; 'link',
  '#url' =&gt; $create_earlywarning_url,
);
return \Drupal::service('renderer')-&gt;renderRoot($link_render_array);


Hope this solves it!