A thin film transistor array panel including a substrate, gate lines and data lines formed on the substrate, and thin film transistors each with a control terminal, an input terminal, and an output terminal. The control and input terminals of the thin film transistor are connected to the gate and data lines. A barrier rib is formed on the gate lines, the data lines, and the thin film transistors. The output terminal of the thin film transistor has an opening, and a portion of the barrier rib formed on the output terminal has an output opening. The barrier rib output terminal portion has the same pattern as the output terminal. A barrier rib for forming contact holes is formed through exposing an organic layer formed on a passivation layer to light from the backside of a substrate using drain electrodes with openings as a light blocking film.