Controllable Efficient 3D/2D Perovskite Polycrystalline Heterojunction for Record‐Performance Mixed‐Cation Horizontal Photodetector

Abstract The 3D/2D perovskite film vertical heterojunction (3D/2D PFVH) has emerged as a promising candidate for high‐performance photodetectors, as it overcomes the limitations of mono‐perovskite while preserving their photoelectric properties and enhancing active layer stability, surface defect passivation, and carrier dynamics. However, controllable and cost‐effective fabrication of efficient 3D/2D PFVH remains challenging. Herein, an improved hot‐pressing reaction transfer‐assisted method is proposed to successfully prepare high‐quality 3D/2D PFVH after optimizing pressure and concentration. A carrier dynamics model is also proposed to elucidate the changes in defect states, carrier dynamics, and photophysical properties during the formation of 3D/2D PFVH. Furthermore, the efficient 3D/2D PFVH under optimal conditions exhibited remarkable enhancements in photoluminescence, carrier lifetime, humidity stability, and defect mitigation. Ultimately, the champion 3D/2D PFVH horizontal photodetector achieved a record‐performance in photo‐responsivity (R up to 4.59 A/W) and external quantum efficiency (EQE up to 1.07 × 10 3 %), signifying their superior light detection capabilities. This study offers valuable insights for designing high‐quality 3D/2D PFVH for advanced high‐performance planar optoelectronic devices for multiple scenes.