Deep‐Red Lasing and Amplified Spontaneous Emission from Nature Inspired Bay‐Annulated Indigo Derivatives

Abstract

While noteworthy progress has been made on organic solid‐state lasers with low amplified spontaneous emission (ASE) thresholds and high optical gains in blue and green colors, the same advancement has not been achieved for red laser dyes. This is mainly due to their low photoluminescence quantum yields (PLQYs) because of “energy bandgap law.” Here, a new family of solution‐processable organic semiconductor laser dyes based on a bay‐annulated indigo derivative (Cibalackrot) with deep‐red emission is reported. They exhibit excellent PLQYs and low ASE thresholds (9.6 µJ cm−2) with deep‐red emission when blended in a mixed host of 1,3‐bis(N‐carbazolyl)benzene (mCP) and 2‐hydroxyphenylbenzothiazole (HBT). In contrast to a single blend in mCP, the co‐blend films are found to significantly enhance the photostability by retaining 90% of initial ASE intensity even after continuous pumping with over 9000 pulses at a pump input energy twice that of the ASE threshold, which can be attributed to efficient cascade energy transfer from mCP to HBT and then to the Cibalackrot chromophore. Low lasing threshold of 6 µJ cm−2 is further achieved at 641 nm by using distributed feedback gratings. Transient absorption spectroscopy measurements indicate that the dye has extremely low yield of triplet excited‐state under optical excitation. The results show Cibalackrot derivatives to be a promising new family of organic deep‐red laser dyes.

Solid cyclooctatetraene-based triplet quencher demonstrating excellent suppression of singlet–triplet annihilation in optical and electrical excitation

“…The first precursor 1 was prepared in a 73% yield from a commercially available 1-bromo-3,5-difluorobenzene with carbazole under nucleophilic aromatic substitution conditions. This was followed by a palladium-catalysed Suzuki-Miyaura cross-coupling reaction with a borane 2 to give 3 (76%), in which 2 was prepared by a hydroboration of 1,5-hexadiene with 9-borabicyclo[3.3.1]nonane (9-BBN) 25 . The similar hydroboration was further conducted for 3 to give borane 4 .…”

Lasing Operation under Long‐Pulse Excitation in Solution‐Processed Organic Gain Medium: Toward CW Lasing in Organic Semiconductors

“…OSLs, including laser operation under short excitation pulses, ranging from 100 femtoseconds (fs) to tens of nanoseconds (ns). [12][13][14][15][16][17][18][19] However, the operation of OSLs under long-pulse excitation of quasi-continuous wave (qCW) or CW regimes remains extremely challenging to achieve, even though it is widely believed as the key stepping stone toward electrically pumped lasers. [13,15,20] The main obstacle of long-pulse OSLs [i.e., millisecond (ms) range] is the indirect generation of triplet excitons (T 1 ) via intersystem crossing (ISC) of radiative singlet excitons.…”

Structural Integration of Carbazole and Tetraphenylethylene: Ultrafast Excited‐State Relaxation Dynamics and Efficient Electroluminescence

“…The precursors 4‐bromophenyl‐4‐hydroxyphenylmethanone [ 17 ] and 9‐(4‐vinylphenyl)‐9 H ‐carbazole [ 18 ] were prepared as per literature sources. Attachment of the solubilizing groups to 4‐bromophenyl‐4‐hydroxyphenylmethanone was achieved by treatment with 1‐bromodecane and potassium hydroxide in anhydrous dimethyl sulfoxide [ 19 ] to give 1 in an 80% yield. 1 was subjected to a McMurry coupling with zinc powder and titanium tetrachloride to give 2 (57%).…”