Circular polarized light (CPL) is an essential light source in many applications, including quantum computation, optical information processing and magnetic recording. Conventional optical CPL detectors rely on achiral photodetector with linear polarizer and quarter waveplate. Such complicated device configuration do not meet the demands of miniaturization trends, which is also incompatible with the emerging wearable technology. How to apply intrinsic chiral semiconductor to detect circularly polarized light is still a great challenge. 

    Organic-inorganic halide perovskites recently emerged as the very promising candidates in optoelectronic application owing to their superior properties. In addition, the versatile structure platform endows perovskites with exceptional features. One of the most striking characteristics is the intrinsic chirality. For example, chiral two-dimensional (2D) perovskites, with the formula of A2PbX4, have been developed by incorporating chiral organic ammonium into the lattice. The resulting chiral 2D perovskites thereby enable CPL detection to become possible. As expected, CPL photodetector based on chiral 2D perovskite single crystals (SCs) and corresponding films have been reported very recently. 

    However, 2D perovskites suffer from strong electron-photon coupling, which introduced nonradiative recombination pathway to deteriorate the materials’ semiconducting properties. As a result, for example, the external quantum efficiency (EQE) for 2D perovskite based light-emitting diodes (PeLED) is still below 1%, which lag far behind their three-dimensional (3D) or reduced-dimensional (quasi-2D) analogues. In addition, 2D perovskites exhibit anisotropic carrier transport features Carrier mobility along the out-of-plane direction is at least one order of magnitude lower than the in-plane direction. Inferior out-of-plane mobility greatly inhibit the carrier transport along this direction, which further impede the charge collection efficiency in corresponding 2D perovskite optoelectronic devices. Therefore, it is necessary to develop new chiral perovskite materials to achieve efficient detection of highly circularly polarized light. 

    Mingjian Yuan’s research group in Key Laboratory of Advanced Energy Materials Chemistry, Ministry of Education (Nankai University), studied chiral quasi-two-dimensional perovskite materials, and systematically proved quasi-2D chiral perovskites do possess intrinsic chirality and have the capability to distinguish CPL photons. Corresponding quasi-2D SCs CPL photodetector exhibit excellent detection efficiency. On this basis, we carefully modulate the film’s crystallization dynamics to facilitate carrier transport. Studies have shown that parallelly oriented perovskite films with homogeneous energy landscape are crucial to maximize the carrier collection efficiency of the resulting chiral quasi-2D perovskite thin-film photodetector. 

    Chiral quasi-2D perovskites possess intrinsic chirality, thus exhibit the capability for advanced CPL detection and directly distinguish between left-handed (LCP) and right-handed CPL (RCP) via electrical signals. The reported flexible chiral quasi-2D perovskite thin-film photodetector exhibits excellent CPL detect efficiency and durability, representing one of the most sensitive and robust CPL detectors to date.  

    The work was recently published in the Angewandte Chemie International Edition by lead author wang Lin, a graduate student at Nankai university. This paper was funded by the national natural science foundation of China (NSFC) 

    Reference: 

    A Chiral Reduced-Dimensional Perovskite for an Efficient Flexible Circularly Polarized Light Photodetector. Lin Wang, Yongxiang Xue, Minghuan Cui, Yanmin Huang, Hongyu Xu, Chaochao Qin, Jien Yang, Haitao Dai, Mingjian Yuan* Angew. Chem. Int. Ed.  https://doi.org/10.1002/anie.201915912