Constructing　a　built-in　electric　field　has　emerged　as　a　key　strategy　for　enhancing　charge　separation　and　transfer,　thereby　improving　photoelectrochemical　performance.　Recently,　considerable　efforts　have　been　devoted　to　this　endeavor.　This　review　systematically　summarizes　the　impact　of　built-in　electric　fields　on　enhancing　charge　separation　and　transfer　mechanisms,　focusing　on　the　modulation　of　built-in　electric　fields　in　terms　of　depth　and　orderliness.　First,　mechanisms　and　tuning　strategies　for　built-in　electric　fields　are　explored.　Then,　the　state-of-the-art　works　regarding　built-in　electric　fields　for　modulating　charge　separation　and　transfer　are　summarized　and　categorized　according　to　surface　and　interface　depth.　Finally,　current　strategies　for　constructing　bulk　built-in　electric　fields　in　photoelectrodes　are　explored,　and　insights　into　future　developments　for　enhancing　charge　separation　and　transfer　in　high-performance　photoelectrochemical　applications　are　provided.　©　University　of　Science　and　Technology　Beijing　2024.