Heavy atom oriented orbital angular momentum manipulation in metal-free organic phosphors

Abstract

Metal-free purely organic phosphors (POPs) are emerging materials for display technologies, solid-state lighting, and chemical sensors. However, due to limitations in contemporary design strategies, the intrinsic spin-orbit coupling (SOC) efficiency...

Metal‐Free Organic Triplet Emitters with On–Off Switchable Excited State Intramolecular Proton Transfer

“…This proximity results in much better utilization of the heavy atom effect compared to isolated Br and carbonyl, [ 38 ] in concordance with the heavy atom oriented orbital angular momentum manipulation effect (HAAM) we recently studied. [ 29 ]…”

“…This proximity results in much better utilization of the heavy atom effect compared to isolated Br and carbonyl, [38] in concordance with the heavy atom oriented orbital angular momentum manipulation effect (HAAM) we recently studied. [29] The strategically created BrA-HBI (Figure 1c,d) with qualitatively distinct low-lying states compared to HBI, where the former's S 1 and T 1 states show considerable (n,π*) character, both in enol and keto forms. In addition, the S 1 states of BrA-HBI have much lower excitation energy compared to that of HBI, corresponding to transitions between the non-bonding (n) and π* orbitals (see NTOs in Figure S1, Supporting Information), given that lone-pair electron orbitals of aldehyde are higher in energy than electrons in the bonding π orbitals.…”

“…RAS-SF is a wave function theory that is well-suited for treating electronically excited states. [35,36] Recent work has enabled RAS-SF to predict accurate SOC elements, [29] making it particularly useful to investigate the prototype ESIPT compounds.…”

“…Considering the complicated four-level photocycle involved, the simplest (2′-hydroxyphenyl)benzimidazole (HBI, 1) scaffold is chosen with subsequent attachment of Br to induce intramolecular heavy atom effect [26] and aromatic carbonyl as the El-Sayed-rule-satisfying unit [27] to create channels for orbital angular momentum migration. [28,29] This strategy is universally applicable to activating efficient triplet population from various ESIPT structures. A thorough photophysical study on the prototype molecules was conducted to elucidate the substitution effects of Br and carbonyl.…”

Decisive role of heavy-atom orientation for efficient enhancement of spin–orbit coupling in organic thermally activated delayed fluorescence emitters

“…Recently, various attempts were made to substitute such heavymetal materials with organic analogues for application in such phosphorescence OLEDs. [6][7][8] However, the best pure organic candidates phosphoresce in the second or millisecond time domain and/or with low quantum yields. [9][10][11] Very recent approaches of incorporation of abundant non-metallic heavy atoms like selenium in organic materials provide submillisecond phosphorescence (385 ms) with a 20% quantum yield.…”