1D/3D Perovskite Heterostructure via Anion Engineering of Ionic Liquids for High-Performance Lateral Photodetectors

Organic-inorganic hybrid perovskites (OIHPs) have emerged as attractive photoactive materials for next-generation photodetectors (PDs) due to their facile solution processability and excellent optoelectronic properties. However, the practical applications of perovskite-based PDs are severely hindered by their intrinsic instability and high dark current. In this work, three kinds of 1-ethyl-3-methylimidazolium-based ionic liquids (ILs) with different (pseudo-) halide anions (including Cl^-, BF₄ ^-, and PF₆ ^-) were utilized to post-treat the top surface of 3D perovskite films, respectively. In particular, the C═N group of 1-ethyl-3-methylimidazolium chloride (EMIMCl) could coordinate with the uncoordinated Pb²⁺ defects on the top surface of the 3D perovskite film, while the chloride anion (Cl^-) effectively passivates the I vacancies defects. In addition, EMIMCl could react with the excess PbI₂ on the top surface of 3D perovskite film to form non-continuous 1D perovskite EMIMPbI₂Cl small islands. Consequently, the EMIMCl-treated perovskite PD demonstrated an ultralow dark current (1.50 × 10^-11 A at a 10 V bias), a high responsivity (0.96 A W^-1), and a high on/off ratio (1.6 × 10⁴). Furthermore, the fabricated bilayer device based on the 1D/3D perovskite heterostructure showed reliable weak-light (0.50 uW cm^-2) detection capability.