Crystallization‐Enhanced Stability by Effectively Suppressing Photooxidation Defect for Optoelectronic Devices. Issue 15 (5th April 2022)

• Record Type: Journal Article
• Authors: Zhang, He; Lin, Dong‐Qing; Liu, Wei; Wang, Yang‐Cheng; Li, Zhu‐Xin; Jin, Dong; Wang, Jin; Zhang, Xin‐Wen; Huang, Lei; Wang, Sha‐Sha; Xu, Chun‐Xiang; Kan, Yu‐He; Xie, Ling‐Hai
• Is Part Of: Advanced materials interfaces. Volume 9:Issue 15(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-04-05
• Subjects: crystalline electroluminescent devices -- crystallization strategy -- molecular wall, organic wide‐bandgap semiconductors -- ultrastable spectra; Materials science -- Periodicals; 620.11
• DOI: 10.1002/admi.202200194
• Languages: English
• ISSNs: 2196-7350

Abstract

Abstract: Effective protection against photooxidation of organic wide‐bandgap semiconductors is a potential method to afford high efficient deep‐blue emission for full color displays. Herein, the crystallization effect of fluorene‐based blue emitter on suppressing the formation of long‐wavelength green band ( g ‐band) defect is demonstrated through the model of self‐assembled organic micro/nanocrystals. The selected molecule 2, 2'‐bi(9, 9‐dipropyl)fluorene (DDC3 F), which easily generates strong g ‐band emission (green index ( I green / I blue ) of ≈5 under ultraviolet exposure for 3 h) in amorphous state, shows an excellent spectra stability of deep‐blue emission with a green index of ≈0 and an unchangeable CIE coordination of (0.18, 0.09) in crystalline nanorod morphologies. Such effect of crystallization‐induced stability enhancement can be further extended into other solution‐processing methods such as brushing. Molecular dynamic simulation reveals that crystalline nanorods with compact molecular packing enable to effectively block the diffusion of O2 and H2 O molecules, which is crucial to suppress the occurrence of photooxidation reactions. Along with high quantum yield of 87% from crystallization‐induced luminescence enhancement effect, such ultrastable deep‐blue emission on crystalline film can also be maintained in solution‐processing organic light‐emitting diode devices. The supramolecular self‐assembled micro/nanocrystals strategy provides a potential platform to maintain ultrastable color purity in organic optoelectronic devices. Abstract : "Molecular packing wall", built from the crystallization strategy, is proposed to suppress photooxidation process and avoid the generation of ketone defects of fluorene‐based semiconductors during the ultraviolet (UV) irradiation. Under the same UV irradiation (≈3 h), the green index ( I green / I blue ) is up to 5 of amorphous film, while the crystalline nanorod film always keep an unchangeable deep‐blue emission with CIE coordination of (0.18, 0.09).