Competitive polarization-enhanced flexophotovoltaic effect in a piezoelectric Janus <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msub> <mml:mi>In</mml:mi> <mml:mn>2</mml:mn> </mml:msub> <mml:mi>STe</mml:mi> </mml:mrow> </

The flexo-photovoltaic (FPV) effect, whereby the induction of a bulk photovoltaic response by a strain gradient, offers a promising mechanism for advanced optoelectronics beyond conventional material symmetries. Here, a pronounced FPV effect in the piezoelectric Janus ${\mathrm{In}}_{2}\mathrm{STe}$ monolayer is reported based on first-principles calculations, where the electronic structure and polarization are exquisitely sensitive to strain gradients. The exceptional flexibility (35.23 N/m), combined with a high out-of-plane piezoelectric coefficient (0.24 pm/V) and a substantial flexoelectric coefficient (4.58 nC/m), underpins strong electromechanical coupling. We harness this to create a polarization-sensitive photodetector that exhibits a self-powered photocurrent via FPV effect, amplified by nearly two orders of magnitude through synergistic piezoelectric-flexoelectric coupling. This coupling can be tuned to a competitive regime, yielding a distinct self-rectifying state. Finally, we integrate these effects to demonstrate dynamic control over photo-carriers, enabling a trichannel optical communication system with enhanced data density. This work establishes a versatile multifunctional coupling architecture for a new generation of intelligent flexible optoelectronics.