Temperature-Regulated Dual Phosphorescence and Mechanical Strain-Induced Luminescence Modulation in a Plastically Bendable and Twistable Organic Crystal

Abstract

A unique, thermally interchangeable, and tunable dual phosphorescence from a single-component organic crystal of DBC (3,6-dibromo-9-ethyl-9H-carbazole) is described here. Temperature-regulated relative intensities of a triple-channel radiative process, viz., singlet and dual triplets, enabled a nearwhite luminescence in a wide temperature range. Interestingly, the single crystals of DBC can also be plastically bent using external mechanical stress and allow the modulation of phosphorescence. The luminescence was completely singlet-mediated in the monomeric state, while the crystalline solid had three pathways of radiative processes. Strong n−π interactions mediated by noncovalent interactions significantly augment the initially forbidden n−π* transitions, which enabled a strong spin−orbit coupling to obtain large radiative triplet states in the solid state. Trapped higher energy triplets were the significant contributors to the emission at lower temperatures, whereas, at higher temperatures, the lower lying triplets dominated the process. A detailed mechanistic approach to unraveling the findings is summarized in the article.

Thermally activated delayed fluorescence in a mechanically soft charge-transfer complex: role of the locally excited state

“…57 Thus, the orbital nature of the singlet and triplet states (LE or CT) is an essential factor determining the efficiency of the ISC (and RISC) process. 5,35,[57][58][59][60][61][62] We consider that for our system, the forbidden RISC (and ISC) are facilitated by the donor-centric locally excited triplet state (LE) T (Fig. 3).…”

“…As a part of our continuous efforts to understand the mechanical properties of organic crystals with fascinating optoelectronic properties, we explored the properties of single crystals of DTBC-TFDCNB and ETC-TFDCNB by performing a sequence of mechanical operations. [35][36][37][38] A schematic representation and optical images of ETC-TFDCNB crystals under mechanical operations are summarised in Fig. 4a-d, S28 and the ESI Videos.…”

Phosphorescence or Delayed Fluorescence? Fate of Excitons in Core-Substituted Naphthalimide-Derived Emitters and Ratiometric Optical Oxygen Sensors

“…Several strategies, including polymerization, crystallization, host–guest interactions, etc. , have been widely attempted to reduce nonradiative loss. − Among these, the most common approach is the dispersion of phosphors in a crystalline polymer matrix which provides a rigid environment by introducing various intermolecular interactions like hydrogen bonding and halogen bonding between phosphor and the polymer matrix. − This doped system also promotes the ISC process by enlarging the SOC constant between the S 1 –T n . − But the environmental rigidity is not enough to suppress the nonradiative relaxation of triplet excitons; the triplet state of molecular oxygen can precisely quench the RTP through triplet–triplet energy transfer between phosphor and oxygen under ambient conditions. The oxygen sensitivity enables one pure organic RTP material to act as a quantitative optical oxygen sensor. − Generally, ratiometric optical oxygen sensors involve multi-luminophores consisting of an oxygen-sensitive phosphor and an oxygen-insensitive fluorophore dispersed in an oxygen-permeable polymer matrix [ e.g.…”

Non‐Covalent Supramolecular 1D Alternating Copolymer in Crystal toward 2D Anisotropic Photon Transport

“…Among these, cavities or lasers, and OWGs are important platforms for constructing miniaturized photonic integrated circuits. In recent years, organic OWGs with adapted functions such as elastic or plastic flexibilities, room temperature phosphorescence, and energy transfer processes have been developed [13–20] …”

“…In recent years, organic OWGs with adapted functions such as elastic or plastic flexibilities, room temperature phosphorescence, and energy transfer processes have been developed. [13][14][15][16][17][18][19][20] Through the use of these components, combinations of heterostructures or hierarchically aligned micro-structures on a large scale have been achieved by self-assembly processes, suitable for applications including organic optical logic gates. [21][22][23][24][25] Moreover, control over the anisotropic transport of photons has attracted much attention for the development of optical logic gates composed of a single component.…”