Strong Polarized Photoluminescence from Stretched Perovskite‐Nanocrystal‐Embedded Polymer Composite Films

Abstract

Polarized light is very necessary to achieve functional optical systems for display, imaging, and information storage. Luminescent materials with polarized emission are of great interest to achieve polarized light. Here, strong polarized photoluminescence from stretched perovskite‐nanocrystal‐embedded polymer composite films is reported by combining an in situ fabrication process with controllable mechanical stretching. The material characterizations show that perovskite quantum dots (QDs) in stretched composite films are oriented aligned into wires along the stretching direction. The optical measurements illustrate that the stretched composite films exhibit not only isotropic absorption but also polarized photoluminescence emission. This feature can be explained with their unique structure of “QD‐aligned wires”. The achieved polarization ratio is consistent with the calculated results by considering the dielectric confinement of optical electric field and exciton–exciton interactions. In addition, the optimized stretched composite films show strong photoluminescence emission with a polarization ratio of up to 0.33 and a quantum yield of 80%. The use of these composite films in liquid crystal display backlights has potential to increase the light transmittance of polarizers from 50% (without considering the optical loss) to 65%, which is of great significance to improve the energy efficiency.

Linearly polarized photoluminescence from anisotropic perovskite nanostructures: emerging materials for display technology

“…For perovskite nanomaterials, the in-situ fabrication features make it easier to be obtained. Lu et al [48] stretched MAPbBr 3 /PVDF polymer composite films via in situ fabrication process in two time nodes corresponding to the crystallization of PVDF and perovskite nanocrystals, the schematic diagram of crystallization process and stretched films at time node 1 and 2 can be seen in Figure 7(a). By applying the TEM characterization, after stretching, the stretched films showed a microstructure of aligned 'QD-aligned wires.'…”

“…The matrix not only oriented the APNCs, but also providing efficient protection against water and oxygen in the air for nanocrystals [57,58]. Stretching of polymer matrix [48,49] and electrospinning [21][22][23][24][25]59] are the most frequently used methods to get aligned APNCs in polymer matrix. For stretching method, Lu et al [48] stretched in-situ fabricated MAPbBr 3 /PVDF composite film and investigated the polarization features of this film.…”

“…Stretching of polymer matrix [48,49] and electrospinning [21][22][23][24][25]59] are the most frequently used methods to get aligned APNCs in polymer matrix. For stretching method, Lu et al [48] stretched in-situ fabricated MAPbBr 3 /PVDF composite film and investigated the polarization features of this film. After stretching, the nanocrystals in the films assembled into 'QD-aligned wires,' which exhibit different relative dielectric constant (3.40) contrast to the surrounding environment (2.02).…”

Robust Hydrophobic and Hydrophilic Polymer Fibers Sensitized by Inorganic and Hybrid Lead Halide Perovskite Nanocrystal Emitters

“…Realization of practical LHP NC emitters is critically dependent upon improving their structural, thermodynamical, and optical stability under ambient conditions, which remains the foremost challenge for such nanomaterials (Huang et al, 2017; Kovalenko et al, 2017; Akkerman et al, 2018; Zhao et al, 2018). Encapsulation of perovskite NCs into macro- or nanoscale polymeric structures has been recently demonstrated (Huang et al, 2016; Raja et al, 2016; Wang et al, 2016, 2017; Hou et al, 2017; Lu et al, 2017; Ma et al, 2017; Murphy et al, 2017; Demkiv et al, 2018; Liao et al, 2018; Lin et al, 2018; Sygletou et al, 2018; Tsai et al, 2018; Wong et al, 2018; Xin et al, 2018; Yang M. et al, 2018; Yang S. et al, 2018; Zhang et al, 2018; Zhu et al, 2018) as simple and low-cost methodologies to preserve the LHP NC chemical integrity by suppressing water and oxygen transmission, improving the thermal stability, and reducing structural modifications, to which LHP NCs are highly susceptible, such as ligand desorption and nanocrystal sintering. Furthermore, integration of the NCs into polymers provides a method to improve their solid-state processability into films, microspheres, fibers, or more complex composites while offering new functionalities such as polarizing PL (Raja et al, 2016; Lu et al, 2017), light detection (Wang et al, 2016), biological labeling and sensing (Wang et al, 2017; Zhu et al, 2018) or device applications such as light emitting diodes (Huang et al, 2016; Liao et al, 2018; Lin et al, 2018; Tsai et al, 2018; Xin et al, 2018; Yang M. et al, 2018; Zhang et al, 2018; Zhu et al, 2018).…”

“…All the studies above employ Cs-based all-inorganic NC sensitizers with the notable exception of refs (Lu et al, 2017; Liao et al, 2018; Yang S. et al, 2018), in which methylammonium lead halide NCs were utilized. On the other hand, the polymer encapsulation of the closely related hybrid analog, but more chemically robust and equally bright formamidinium lead halide NCs (Protesescu et al, 2016, 2017) has not received much attention.…”