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

ABSTRACT 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 − , BF 4 − , and PF 6 − ) 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 Pb 2+ 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 PbI 2 on the top surface of 3D perovskite film to form non‐continuous 1D perovskite EMIMPbI 2 Cl 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 × 10 4 ). Furthermore, the fabricated bilayer device based on the 1D/3D perovskite heterostructure showed reliable weak‐light (0.50 uW cm −2 ) detection capability.