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.

The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/solr.202200609.

Perovskite Films In article number http://doi.wiley.com/10.1002/solr.202200609, Pei‐Ting Chiu and co‐workers found that the proportion of the facet (001) of PbI2 crystals increases as the synthesis temperature increases and fabricates better formamidinium‐based perovskite films. The perovskite solar cells based on the PbI2 synthesized at 120 °C exhibit the best power conversion efficiency (PCE) of 17.96% and the module with an active area of 3.68 cm2 shows a PCE of 16.08%.