Crystallization‐Enhanced Stability by Effectively Suppressing Photooxidation Defect for Optoelectronic Devices

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 (DDC3F), which easily generates strong g‐band emission (green index (Igreen/Iblue) 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 H2O 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.

C-H-activated Csp2-Csp3 diastereoselective gridization enables ultraviolet-emitting stereo-molecular nanohydrocarbons with mulitple H•••H interactions

“…5f). These observations suggested that DWG1 exhibited crystal-induced luminescence enhancement feature, [46][47][48][49] while TWG1 did not, probably due to its tighter arrangement in the crystalline (the density of single crystals: 1.335 gcm -3 , 1.296 gcm -3 , 1.238 gcm -3 and 1.081 gcm -3 for meso-DWG, rac-DWG1, cis-cis-TWG1 and cis-trans-TWG1, respectively) and strong intermolecular interactions, effectively suppressing the nonradiative relaxation process. Interestingly, these results contradict the phenomenon of red-shifted and quenched emission observed in most luminescence due to exciton coupling, orbital overlap, and π-π aggregation as pressure increases.…”

Recent Advances in Low‐Dimensional Nanomaterials for Photodetectors

“…Reproduced with permission. [186] Copyright 2022, Wiley-VCH. c) High-resolution XPS spectra of Zn 2p, Cd 3d, and S 2p of ZnS, Cd 0.4 Zn 0.6 S, and CdS based 1D NRs.…”

Multicolor Emission of Organic Microcrystals with Charge Transfer Interactions through Cocrystal Engineering

“…Recently, organic functional materials exhibit a wide range of promising applications in various devices with the unique combination of tunable optoelectronic properties, such as organic light-emitting diodes (OLEDs), − organic photovoltaics (OPVs), − organic lasers, − organic field-effect transistors (OFETs), − and even organic field-effect light-emitting transistors. − In particular, the organic crystalline materials have been demonstrated to be more significant for enhanced device performance with features of minimized impurities and ordered molecular arrangement. , In general, the emission color of crystalline materials is both determined by molecular structures and aggregate states, which can be further finely tuned by modification of the molecular fragment or regulation of packing modes based on the noncovalent supramolecular interaction in the same building block. − In fact, compared with the traditional and tedious structure synthesis based on covalent bonds, the regulation of molecular packing in the crystalline state is a simpler and lower cost method . For single-component crystalline materials, the multicolor emissive behaviors can be obtained in the polymorph states due to the different molecular conformations, through induction of solvent molecules. − However, the phenomenon is extremely limited and difficult for aggregate chemistry. , Therefore, a simple and universal method specifically needs to be established to achieve multicolor emission in organic crystalline materials.…”