Sequential Growth of 2D/3D Double‐Layer Perovskite Films with Superior X‐Ray Detection Performance

Perovskite materials in different dimensions show great potential in direct X-ray detection, but each with limitations stemming from its own intrinsic properties. Particularly, the sensitivity of two-dimensional (2D) perovskites is limited by poor carrier transport while ion migration in three-dimensional (3D) perovskites causes the baseline drifting problem. To circumvent these limitations, herein a double-layer perovskite film is developed with properly aligned energy level, where 2D (PEA)₂ MA₃ Pb₄ I₁₃ (PEA=2-phenylethylammonium, MA=methylammonium) is cascaded with vertically crystallized 3D MAPbI₃ . In this new design paradigm, the 3D layer ensures fast carrier transport while the 2D layer mitigates ion migration, thus offering a high sensitivity and a greatly stabilized baseline. Besides, the 2D layer increases the film resistivity and enlarges the energy barrier for hole injection without compromising carrier extraction. Consequently, the double-layer perovskite detector delivers a high sensitivity (1.95 × 10⁴ μC Gy_air ^-1 cm^-2 ) and a low detection limit (480 nGy_air s^-1 ). Also demonstrated is the X-ray imaging capacity using a circuit board as the object. This work opens up a new avenue for enhancing X-ray detection performance via cascade assembly of various perovskites with complementary properties.