Tableting Engineering in Halide Gradient Perovskite: Energy Band Regulation and Design of Carrier Dynamics for THz Sensing

Abstract

Component regulation in perovskite single crystals (SCs) sets the precondition for designing energy band and carrier dynamics, which is essential for exploring functional optoelectronic devices. However, entropy‐driven ion diffusion in SCs leads to component homogenization in a few hours, while the gradient films exhibit long‐term gradient stability. Therefore, tableting engineering is proposed to introduce appropriate boundaries, ensuring good short‐range alignment within the grains and suppressed ion diffusion in the long range. With 6–10 MPa pressure, transverse/longitudinal gradient MAPbX3 (X = Cl, Br, I) tablets are constructed. Due to the alignment of the valence band maximum from MAPbCl3 to MAPbBr3 to MAPbI3, the hole extraction is significantly promoted. As well, different metal electrodes are utilized to regulate the main carrier types. Hole‐type Au/gradient tablet/Au devices show an obvious rectification effect, while electron‐type Ag/gradient tablet/Ag devices have near‐Ohmic contact. Compared to the electron‐type devices, Au/gradient tablet/Au devices show a 3.9‐fold improvement in terahertz responsivity to 3.51 µA W−1, a 2.6‐fold reduction in noise‐equivalent power to 2.22 × 10−8 W Hz−1/ 2; and a 2.6‐fold increase in specific detectivity to 1.89 × 107 Jones. This work demonstrates the tableting engineering to realize stable compositional gradients for energy band regulation in weak‐signal THz detection.