Progress and Perspective toward Continuous‐Wave Organic Solid‐State Lasers

Abstract

A continuous‐wave (CW) organic solid‐state laser is highly desirable for spectroscopy, sensing, and communications, but is a significant challenge in optoelectronics. The accumulation of long‐lived triplet excitons and relevant excited‐state absorptions, as well as singlet–triplet annihilation, are the main obstacles to CW lasing. Here, progress in singlet‐ and triplet‐state utilizations in organic gain media is reviewed to reveal the issues in working with triplets. Then, exciton behaviors that inhibit light oscillations during long excitation pulses are discussed. Further, recent advances in increasing organic lasing pulse widths from microseconds toward the indication of CW operation are summarized with respect to molecular designs, advanced resonator architectures, triplet scavenging, and potential triplet contribution strategies. Finally, future directions and perspectives are proposed for achieving stable CW organic lasers with significant triplet contribution.

Double-locked narrowband hybrid locally-excited and charge-transfer emitter exhibiting amplified spontaneous emission

“…At low excitation power from 0.76 to 3.95 μJ cm −2 , the spectra detected from the edge emission were identical to that of the steady-state PL, indicating the optical-pumping intensity was below the threshold. [39][40][41] Noticeably, with the further increase of the excitation power up to 24.2 μJ cm −2 , the abrupt narrowing of spectral FWHMs from 47 to 11 nm, as well as the rapid nonlinear increase of output intensity occurred. Thus, a low ASE threshold of 5.7 μJ cm −2 was determined.…”

Light blue rigid excited-state intramolecular proton transfer organic semiconductor laser chromophores

“…Organic laser materials are capable of exhibiting amplified spontaneous emission (ASE). 17,18 Broadly, ASE demonstrates whether energy gains exceed energy losses within a given system. Over last decades, great efforts have been made on the development of different classes of efficient organic laser dyes to achieve low ASE and laser thresholds, 19–25 laser operation under long pulse excitation, 13,26 efficient triplet quenchers, 27–30 and high stability of laser dyes at the molecular level as well as the harness of triplets.…”

A Rigid Multiple Resonance Thermally Activated Delayed Fluorescence Core Toward Stable Electroluminescence and Lasing

“…With the significant advancements in organic light‐emitting molecules, the aggregation‐caused quenching was suppressed, which led to the evolution of organic lasings from solution state to solid state [5,6,12–14] . In order to advance toward organic continuous‐wave (CW) and even electrically‐pumped laser devices, efforts have been focused on molecular design and exciton (singlet, triplet, and polaron) manipulation to enhance the stimulated emission coefficient and mitigate photon loss caused by interior quenching and excited‐state absorptions [15–20] . In the past two decades, a series of derivatives from fluorene and bis‐stilbene units, such as poly(9,9‐dioctylfluorene) (PFO), [17] 4,4’‐bis[(N‐carbazole)styryl]biphenyl (BSBCz), [21] bis(N‐carbazolylstyryl)‐9,9‐dihexylfluorene (BSFCz), [22] and 4,4’‐bis[4‐(diphenylamino)styryl]biphenyl (BDAVBi), [23] have been developed to prolong the pulse width under optical excitation.…”

“…[5,6,[12][13][14] In order to advance toward organic continuous-wave (CW) and even electrically-pumped laser devices, efforts have been focused on molecular design and exciton (singlet, triplet, and polaron) manipulation to enhance the stimulated emission coefficient and mitigate photon loss caused by interior quenching and excited-state absorptions. [15][16][17][18][19][20] In the past two decades, a series of derivatives from fluorene and bis-stilbene units, such as poly(9,9-dioctylfluorene) (PFO), [17] 4,4'-bis[(Ncarbazole)styryl]biphenyl (BSBCz), [21] bis(N-carbazolylstyryl)-9,9-dihexylfluorene (BSFCz), [22] and 4,4'-bis [4-(diphenylamino)styryl]biphenyl (BDAVBi), [23] have been developed to prolong the pulse width under optical excitation. Benefitting from its large stimulated emission coefficient (> 1�10 À 16 cm 2 ), and the suppression of excitedstate absorptions, including singlet absorption (S 1 !S n ), triplet absorption (T 1 !T n ), and polaron absorption (P!P*) etc., BSBCz and poly(2,5-bis(2',5'-bis(2''ethylhexyloxy)phenyl)-p-phenylenevinylene) (BBEHP-PPV) have successfully indicated a direct and indirect electrically-pumped distributed feedback resonator (DFB) laser device, respectively.…”