Vertical‐type 3D/Quasi‐2D n‐p Heterojunction Perovskite Photodetector

Abstract This research demonstrates a state‐of‐the‐art vertical‐transport photodetector with an n‐type 3D MAPbI₃/p‐type quasi‐2D (Q‐2D) BA₂MA₂Pb₃I₁₀ perovskite heterojunction. This structure introduces a ≈0.6 V built‐in electric field at the n‐p junction that greatly improves the characteristics of the perovskite photodetector, and the presence of Q‐2D perovskite on the surface improves the life. The electrical polarities of the 3D and the Q‐2D perovskite layers are simply controlled by self‐constituent doping, making clearly defined n‐p characteristics. Doctor‐blade coating is used to fabricate the photodetector with a large area. The Q‐2D materials with highly oriented (040) Q‐2D (n = 2,3) planes are near the surface, and the (111) preferred planes mixed with high index Q‐2D materials (n = 4,5) are found near the 3D/Q‐2D interface. The stacking and interface are beneficial for carrier extraction and transport, yielding an external quantum efficiency of 77.9%, a carrier lifetime long as 295.7 ns, and a responsibility of 0.41 A W⁻¹. A low dark current density of 6.2 × 10⁻⁷ mA cm⁻² and a high detectivity of 2.82 × 10¹³ Jones are obtained. Rise time and fall time are fast as 1.33 and 10.1 µs, respectively. The results show the application potential of 3D/Q‐2D n‐p junction perovskite photodetectors.