Chirality‐Dependent Circular Photogalvanic Effect in Enantiomorphic 2D Organic–Inorganic Hybrid Perovskites

Abstract

The circular photogalvanic effect (CPGE) is a novel spin-related optoelectronic phenomenon based on the SOC of noncentrosymmetric systems. [15] Under the CPGE, a steady photocurrent is generated by the irradiation of circularly polarized light (CPL) without an external bias voltage, and the photocurrent direction is reversed by switching the photon helicity. [15,16] The CPGE originates from the asymmetric distribution of photocarriers in a momentum space (k-space) excited by CPL in interband transitions with a spin-flip between the spin-splitting states (Scheme 1). [16] The direction of the zero-bias photocurrent can be controlled based on the helicity of the CPL, as the asymmetric distribution of photocarriers arises from the selection rule of CPL excitation, Δm J = ±1, where m J is the magnetic quantum number of the total angular momentum (Scheme 1). [16] Hence, noncentrosymmetric systems, wherein SOC could induce spin-splitting in electronic states, are promising platforms to generate the CPGE. In fact, the CPGE has been observed in various polar systems, such as group III-V compound semiconductors, [16][17][18][19] the surface of topological insulators, [20][21][22] a bulk Rashba semiconductor, [23] and transition metal dichalcogenides. [24][25][26][27] In these studies, the correlation between polarity and the CPGE was investigated in detail, andThe control of the optoelectronic properties of 2D organic-inorganic hybrid perovskite (2D-OIHP) lead halides is an increasingly prevalent topic. Herein, the observation of the circular photogalvanic effect (CPGE) in new enantiomorphic 2D-OIHP lead iodides is reported, which are synthesized as a first OIHP-related system belonging to a chiral space group by incorporating organic chiral cations into the inorganic layers of lead iodides. The CPGE is an optoelectronic phenomenon associated with the spin-orbit coupling of heavy atoms in noncentrosymmetric systems. Owing to the CPGE, lighthelicity-dependent steady photocurrents are generated without an external bias voltage under the irradiation of circularly polarized light. Furthermore, the sign reversal of the CPGE photocurrent depending on the chirality of the designed 2D-OIHP lead iodides is observed. This result indicates formation of the theoretically predicted radial spin-polarized texture in k-space of chiral systems owing to spin-momentum locking. Hence, chiral 2D-OIHP lead halides can be a promising platform for engineering opto-spintronic functionalities.

Heterogeneous Integration of Chiral Lead–Chloride Perovskite Crystals with Si Wafer for Boosted Circularly Polarized Light Detection in Solar‐Blind Ultraviolet Region

“…Continuously rotating the λ/4 plate from 0° to 360°, the incident light (266 nm, 35 mW cm −2 ) is tuned from linear to elliptical, and eventually to circular at φ = ±π/4. [40,41] Before measurement, we have carefully calibrated the system to ensure the same intensity of polarized light illumination in the experiment. We note that because the device is operated under zero bias, the SC is produced only by light absorption.…”

Recent Progress on Two-Dimensional Materials

“…So far, many types of 2D materials have been fabricated into chiral ones, including the 2D perovskites 302,[663][664][665][666][667][668][669][670] , graphene [671][672][673] , TMDs [674][675][676][677] , 2D organic nanoassemblies 678 and many more. A key scientific issue is how the chirality is originated and how to endow the 2D materials with chirality.…”

1D Chiral Lead Halide Perovskites with Superior Second‐Order Optical Nonlinearity

“…[ 14 ] Since then, chiral hybrid perovskites have attracted extensive research interest and become a type of important materials owing to their unique chiroptical properties. [ 15–17 ] They have emerged as promising materials for wide applications in many fields ranging from circularly polarized photodetectors [ 18–21 ] and circularly polarized light‐emitting materials [ 22–25 ] to spintronic devices. [ 26–28 ] In particular, the introduction of chiral components often induces intrinsic noncentrosymmetric and polar structures of the resulted perovskites, which offers endless possibilities for the preparation of intriguing crystal structures with highly efficient ferroelectric [ 29–34 ] and second‐order NLO properties.…”