dom pdf not working in pdf download codeigniter 2

I tried to download bill in my application. I am using dom pdf library to download pdf .

In general static file pdf download working.

When i make it as dynamic pdf download not working. it just view the template part in browser pdf not download

function pdf_download($bill_id){ 
    
    $this->load->library('pdf');  
    $filename = "Document_name";
         
     $finaldata['note_info']  = $this->get_data($bill_id);  
         
    $html = $this->load->view('mail_bill', $finaldata, TRUE);

    $this->pdf->create($html, $filename);
    }