Superlattices (SLs) based on colloidal nanocrystals (NCs) represent a fascinating structure with long-range and ordered NCs inside the assembled superstructures, displaying great potential application in electronic devices because of the customizable arrangement of building blocks. It is a great challenge to achieve macroscopical SL films by a solution process due to the inherent sensitivity and difficulty in controlling colloidal NCs. In this study, we propose a controllable strategy to create perovskite CsPbBr3 NC SL films through a surface in situ cross-linking reaction incorporating conjugated linoleic acid (CLA), a naturally polymerizable small molecule. CLA enables the in situ cross-linking of adjacent NCs under polarity-triggered conditions, which effectively arranges the NCs in a solid form at a molecular level to achieve fcc SL structural films. Importantly, we report for the first time NC SL films that are simultaneous with outstanding intrinsically linearly polarized emission and orderly electric polarity, which are derived from consistent dipole alignment, thus showing promising potential for application in information storage and optoelectronics. This method provides a general bottom-up approach, expanding the assembly library for fundamental studies and technological applications.
Although quasi-two-dimensional (quasi-2D) perovskites are ideal material platforms for highly efficient linearly polarized electroluminescence owing to their anisotropic crystal structures, so far, there has been no practical implementation of these materials for the demonstration of linearly polarized perovskite light-emitting diodes (LP-PeLEDs). This scarcity is due to difficulty in orientation and phase distribution control of the quasi-2D perovskites while minimizing the defects, all of which are required to manifest aligned transition dipole moments (TDMs). To achieve this multifaceted goal, herein, we introduce a synergistic strategy to quasi-2D perovskites by incorporating both a trimethylolpropane triacrylate anchoring layer and 18-Crown-6 molecular passivator into the film fabrication process. It is found that the interfacial anchoring layer guides the oriented growth of perovskites along the (110) plane, whereas the molecular passivator reduces the number of defects and homogenizes the crystal phase. As a result, a quasi-2D perovskite film with macroscopically aligned TDM that renders high radiative recombination and the degree of linear polarization (DoLP) is constructed. This “coherence-programmed emission layer” demonstrates highly efficient LP-PeLEDs, not only achieving a maximum external quantum efficiency of ∼23.7%, a brightness of ∼36,142 cd/m2, and a DoLP of ∼38%, but also significantly improving the signal-to-interference-and-noise ratio in a multi-cell visible light communication system.
Ziheng Wang,Xueying Chu,Jinhua Li,Zhankun Weng,Mingze Xu,Yingjiao Zhai,Li Ma,Xiaojun Wang
The polarization-sensitive optical properties of semiconductor nanorods (NRs) are attractive characteristics for optical devices . Although oriented NR films can provide convenient integration and new application opportunities, the realization of large-area NR films with polarized photoluminescence (PL) remains a challenge. Herein, we fabricated ordered CdSe/CdS NR films on an arbitrary substrate using the Langmuir-Blodgett technology. Polarization-sensitive PL was observed for the NR films. The band-edge exciton fine structure owing to the rod-like morphology and the dielectric effect of the orderly arranged NRs were discussed with a focus on the contribution to polarized photons. The degree of linear polarization of the CdSe/CdS NR films excited a circularly polarized light was approximately 0.30. When linearly polarized ultraviolet (UV) light was used as the excitation source, the PL intensity of the NR films periodically varied with the polarization direction of the UV light. The corresponding PL polarization (i.e., “excitation polarization”) was approximately 0.28. The polarization-sensitive fluorescence (approximately 526 nm) excited by the UV-polarized light (325 nm) demonstrates the potential for realizing low-cost polarization-sensitive devices using only a visible light charge-coupled device system.
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