In Situ Green Preparation of Highly Stable CsPbBr₃–Polyimide Films for Flexible Liquid Crystal Displays

Abstract

Inorganic lead halide perovskite quantum dots (QDs) CsPbX3 (X = Cl, Br, or I) with superior optical and electronic properties are regarded as excellent materials for various optoelectronic devices. However, their instability significantly hinders their practical applications. Herein, composite films of CsPbBr3 QDs and polyimide (CsPbBr3@PI) are prepared using an in situ green synthesis method without other ligands and anti‐solvents. This strategy allows the formation of CsPbBr3 QDs and polymerization of polyimide monomers to occur simultaneously, which encapsulates the CsPbBr3 QDs with a protective PI layer. The CsPbBr3@PI film has narrowband green emission and excellent stability against air, water, and light. The emission intensity of a CsPbBr3@PI film is maintained at 93% and 90% of the initial intensity after exposure to air for 43 days and immersion in water for 14 days, respectively. In addition, the water contact angle is 105°, indicating that the film has good hydrophobicity. Surprisingly, the film is not broken after repeated bending (1 250 times), and its emission intensity is almost unchanged, which illustrates that the film has excellent flexibility. The good performance of the obtained CsPbBr3@PI films indicates their potential as a backlight source for flexible liquid crystal display applications.

NondemandingIn SituEncapsulation Route to Ultrastable Perovskite Nanocrystals for White Light-Emitting Diodes

“…52,53 Although the stability of PNCs synthesized from this approach may not be as high as that of PNCs fabricated from inorganic coating strategies because PNCs were not fully covered by insulating ligands, a reasonable balance was made between the structural stability and electron/hole transportation property, which was essential for the high-performance PNC-based optoelectronics. 54,55 Moreover, macromolecule passivation, including polyimide, 56 polyacrylonitrile, 57 and polyfluorene suppressing the halide ion migration, 58 was found to be equally advantageous to enhancing PNC stability by suppressing the halide ion migration or forming coordination interaction for potential applications in CO 2 conversion, wide-color gamut displays, light-emitting diode (LED) devices, 59 and stretchable displays. 60,61 In addition to homopolymers, well-defined synthetic linear 61−64 and star-like block copolymers 65 with controlled molecular weight, pre-designed compositional architecture, and functionality were utilized to obtain highly stable PNCs owing to their ability to coordinate with surface atoms on PNCs to maintain colloidal stability, fill the traps to achieve the high PLQY, and form a condense protection shield on PNCs to maintain moisture stability.…”

“…by constructing inert shielding on the surface of PNCs to prevent the perovskite crystal structure from being damaged by external perturbations and preserve optical properties. Surface-capping ligand engineering based on small molecules (e.g., semiconducting molecule, metal complex, organic sulfonium bromide, inorganic metal salt, and zwitterionic molecule) was identified as another efficacious approach for strongly anchoring on the PNCs to repair the surface defects of PNCs, thereby addressing the ligand thermodynamic instability issue of originally capped oleylamine (OAm) or oleic acid (OA) while increasing the various stabilities of PNCs (even in water) with high PLQY. , Although the stability of PNCs synthesized from this approach may not be as high as that of PNCs fabricated from inorganic coating strategies because PNCs were not fully covered by insulating ligands, a reasonable balance was made between the structural stability and electron/hole transportation property, which was essential for the high-performance PNC-based optoelectronics. , Moreover, macromolecule passivation, including polyimide, polyacrylonitrile, and polyfluorene suppressing the halide ion migration, was found to be equally advantageous to enhancing PNC stability by suppressing the halide ion migration or forming coordination interaction for potential applications in CO 2 conversion, wide-color gamut displays, light-emitting diode (LED) devices, and stretchable displays. , In addition to homopolymers, well-defined synthetic linear − and star-like block copolymers with controlled molecular weight, pre-designed compositional architecture, and functionality were utilized to obtain highly stable PNCs owing to their ability to coordinate with surface atoms on PNCs to maintain colloidal stability, fill the traps to achieve the high PLQY, and form a condense protection shield on PNCs to maintain moisture stability. Apart from stability enhancing strategies via surface coating or surface ligand engineering, substitution of the A or B site element in the perovskite structure with dopants, , generation of a halide-rich surface, and in situ formation in the natural product were also proven to be effective for preserving perovskite phase stability and thermal stability without sacrificing the optical property, which were favorable to PNC-related devices requiring excellent charge-transport properties.…”

Highly efficient CsPbBr3@glass@polyurethane composite film as flexible liquid crystal display backlight

“…In particular, with the development of flexible liquid crystal display (LCD) technology, the demand for flexible backlight sources is gradually increasing. In recent years, there have been many studies on PQDs dispersed in organic poly-mers to prepare flexible luminescent films, such as CsPbBr 3 dispersed in polyimide (PI), 29 ethylene-vinyl acetate (EVA) copolymers, 30 TFE-HF, 31 and so on. Therefore, it would be meaningful to combine the PQD glass with organic polymers to prepare flexible luminescent films.…”

Shape-controlled synthesis of one-dimensional cesium lead halide perovskite nanocrystals: methods and advances

“…These features enable MHP NCs to have huge potential applications in optical devices, photovoltaics, lasers, photodetectors, light-emitting diodes, liquid crystal displays, biological imaging, sensors, and photocatalysis. 6–15…”

“…These features enable MHP NCs to have huge potential applications in optical devices, photovoltaics, lasers, photodetectors, lightemitting diodes, liquid crystal displays, biological imaging, sensors, and photocatalysis. [6][7][8][9][10][11][12][13][14][15] Cesium lead halide perovskite nanocrystals (CsPbX 3 NCs) are one of the most representative MHP NCs. In the past several years, considerable research effort has been devoted to their synthesis and morphology/shape control.…”