Tunable Triplet-Mediated Multicolor Lasing from Nondoped Organic TADF Microcrystals

Abstract

Thermally activated delayed fluorescent (TADF) emitters have received great attention in organic light-emitting diodes and laser diodes because of high exciton utilization efficiency and low optical loss caused by triplets. However, the direct observation of lasing emission from nondoped TADF microcrystals has yet to be reported. Here, we demonstrated a three-color (green, yellow, and red) microlaser from three nondoped TADF microcrystals with well-controlled geometries. The temperature-dependent dynamic analyses testify that the regenerated singlets which originated from the reverse intersystem crossing process at room temperature are beneficial for population inversion and reduce tripletabsorption/annihilation optical loses, together resulting in thermally activated lasing actions. Thanks to single-crystalline structures of TADF emitters, the relationship between triplet-harvesting capability and the molecular structure was systematically investigated. The results not only offer rational design of pure TADF gain materials but also provide guidance for the high-performance electrically driven organic solid-state lasers and multicolor laser integration.

Self‐Erase Force‐Induced Turn‐On Organic ASE Output Cryptographic Primitive for Advanced Multiple Information Encryption

“…In addition, two microcrystals exhibit as active optical waveguides with brighter PL edge and weaker PL from the bodies (Figure 1b and Figure S3, Supporting Information), which shows that they might potentially serve as active media for both PL emission and optical resonators. [ 34 ] It should point out that the state‐of‐the‐art PCF materials often require a pressure of GPa level to achieve luminescence and/or intrinsic color regulation, [ 29,30 ] which caused the destruction of crystal morphology and restricted their practical applications. We demonstrated that the fluorescence switching of TPIZ microcrystals can be achieved under only 1.0 MPa, while the retentive crystal morphology provided the possibility of TPIZ as a candidate for force‐induced laser output.…”

Thermally Activated Delayed Fluorescent Gain Materials: Harvesting Triplet Excitons for Lasing

“…Further progress has been made in recent years. [43][44][45][46][47][48][49][50][51][52] Since the first attempt to use TADF materials in OLEDs, [53,54] various TADF materials have been designed and synthesized. [55][56][57] However, only some of these materials have been reported to exhibit laser activity.…”

“…[55][56][57] However, only some of these materials have been reported to exhibit laser activity. [43][44][45][46][47][48][49][50][51][52] The relationship between the molecular structures of TADF materials and their laser properties remains unclear. Recent progress in TADF gain materials is reviewed in this paper to illustrate the recent advances in TADF gain materials, raise awareness of this new field and extract the fundamental design principles and strategies of TADF gain materials.…”

The Second Excited Triplet‐State Facilitates TADF and Triplet–Triplet Annihilation Photon Upconversion via a Thermally Activated Reverse Internal Conversion

“…Therefore, the T 2 state involved in the TADF mechanism has begun to draw increased attention. The incipient criterion of the T 2 -mediated TADF channel in a few studies only concentrates on both the sufficiently small splitting energy |ΔE S1-T2 | (|ΔE S1-T2 | < |ΔE S1-T1 |) and large SOC value between S 1 and T 2 , [13,14] without considering the T 2 − T 1 gap. Afterward, some studies have shown that the T 2 -mediated T 1 → T 2 → S 1 TADF channel (Scheme 1c) is formed by populating T 2 excitons from T 1 through Boltzmann statistics, spin−vibronic coupling, and reverse internal conversion (RIC) on the basis of a narrow T 2 − T 1 gap.…”