Space-Isolated Chromophore for Organic Blue Phosphorescence with High Efficiency and a Deep-Blue Lasing Characteristic.

High-efficiency blue phosphorescence and deep-blue laser emissions play a crucial role in organic optoelectronic applications. However, designing metal-free organic blue luminescence with high energy levels of excited states and suppression of nonradiative transitions remains a formidable challenge. Herein, we demonstrate a synthetic strategy for achieving a deep-blue laser and efficient phosphorescence based on confining chromophores in the tetrahedral structure of sp3 hybridization. The data analysis reveals that the construction of the quaternary carbon center contributes to spatially separated donors and acceptors and considerable steric constraints, prompting an effective intersystem crossing (ISC) process and suppressing nonradiative transitions. The negligible interaction between chromophores simultaneously produces a deep-blue fluorescent laser and blue phosphorescence with an efficiency up to 82.3%. This work opens the door to multifunctional blue-emitting materials with high efficiency, providing a high-potential candidate for electrically pumped organic lasers and energy efficient light-emitting diodes.

Organic Phosphorescence Lasing Based on a Thermally Activated Delayed Fluorescence Emitter.

Organic phosphorescence materials provide an opportunity to use triplets for lasing. However, population inversion based on phosphorescence is hard to establish, owing to low luminescent quantum efficiency and intensive optical loss. By comparison, thermally activated delayed fluorescence emitters exhibit excellent optical gain with the aid of the reverse intersystem crossing (RISC) process. In this work, we designed a multifunctional gain material, not only serving as a thermally activated delayed fluorescence (TADF) emitter with excellent optical gain but also working as a phosphorescence source with high utilization of triplets. The lone pair of electrons in oxygen substitutions promotes a fast spin-flip and high delayed fluorescence quantum yield (ΦDF = 55%), enabling TADF amplified spontaneous emissions (ASE) of CH2Cl2 solution. Single-crystalline nanowires of H-aggregates effectively lower triplet energy levels with high phosphorescence quantum yield (ΦP = 27%), demonstrating Fabry-Perot mode phosphorescence lasing at 630 nm.