Epitaxy of a Monocrystalline CsPbBr₃–SrTiO₃ Halide–Oxide Perovskite p–n Heterojunction with High Stability for Photodetection

Abstract Perovskite heterojunctions are essential components of perovskite optoelectronics, but their construction and investigation have been impeded by the instability and severe anion interdiffusion. This work epitaxially deposits p‐type CsPbBr₃ on n‐type Nb:SrTiO₃ (STO) to construct a functional perovskite heterojunction with high stability. The lattice match allows epitaxial growth of CsPbBr₃ to occur over large scale, resulting in a monocrystalline thin film with excellent crystallinity and uniformity. The highly stable STO prevents the anion migration frequently happening in halide perovskites, forming a sharp interface of two perovskite with opposite conduction type, with which a diode is fabricated and a current rectification ratio of 374 is obtained. The diode is able to work as a photodetector with dark current of 2.01 × 10⁻¹² A at −1 V and responsivity (R) of 8.26 A W⁻¹, rendering a detectivity (D*) of 2.98 × 10¹³ Jones. Owing to the all‐inorganic architecture, effective photoresponse at temperature as high as 150 °C is guaranteed with D* of ≈1.52 × 10¹³ Jones. Combining the unique optoelectrical properties of halide perovskite and the rigidity of oxide perovskite, the epitaxy of CsPbBr₃ on n–type STO opens up a new method to construct functional perovskite heterojunction for optoelectronics.