Synergistic Pyro‐Phototronics and Structural Anisotropy in CsAg ₂ I ₃ /GaN Heterostructures for High‐Performance Polarization‐Sensitive UV Photodetectors

Ultraviolet photodetectors capable of spectral selectivity, self-powered operation, and polarization sensitivity are vital for next-generation secure communication and sensing, yet their progress is hampered by material instability, interfacial losses, and the difficulty of multifunctional integration. Here, we report a groundbreaking CsAg₂I₃/GaN van der Waals (vdWs) heterojunction that uniquely integrates in-plane structural anisotropy, pronounced pyro-phototronic effect, and atomically sharp interface engineering. The CsAg₂I₃ single-crystals, synthesized via chemical vapor deposition, exhibit a wide-bandgap (∼3.38 eV), strong second-order nonlinear response, and remarkable pyroelectricity, overcoming the stability and symmetry limitations of conventional perovskites and inorganic wide-bandgap semiconductors. The CsAg₂I₃/GaN device delivers record-breaking performance: an ultralow dark current of 0.3 pA, high responsivity of 0.28 A/W, specific detectivity of 1.7 × 10¹² Jones, and ultrafast response speeds of 16/21 µs, outperforming most state-of-the-art perovskites and wide-bandgap photodetectors. Crucially, the pyro-phototronic effect amplifies polarization sensitivity, achieving an unprecedented dichroic ratio of 10.5 under bias, the highest reported for all-inorganic perovskite systems and other competitors. The device also demonstrates exceptional operational stability and robust performance in an information-splitting encryption system, validating its real-world applicability. This work establishes a new paradigm for synergizing pyro-phototronics and structural anisotropy in heterostructures, enabling a versatile platform for high-performance, self-powered, polarization-sensitive optoelectronics.