This review introduces the design, opportunities, and challenges of organic gain media for organic solid-state lasers, especially for organic semiconductor lasers, providing a clear panorama for this interesting and exciting research field.

Covalent organic frameworks (COFs) have served as a family of porous crystalline molecules for various promising applications. However, controllable synthesis of COFs with uniform morphology is paramount yet still remains quite challenging. Herein, we report self-templated synthesis of uniform and unique hollow spheres based on highly conjugated three-dimensional (3D) COFs with diameters of 500–700 nm. A detailed time-dependent study reveals the continuous transformation from initial nano sphere-like particles into uniform hollow spherical structures with Ostwald ripening mechanism. Particularly, the resulting 3D COF (3D-Sp-COF) is prone to transport ions more efficiently and the lithium-ion transference number (t+) of 3D-Sp-COF reaches 0.7, which even overwhelms most typical PEO-based polymer electrolytes. Inspiringly, the hollow spherical structures show enhanced capacitance performance with a specific capacitance of 251 F g−1 at 0.5 A g−1, which compares favorably with the vast majority of two-dimensional COFs and other porous electrode materials.

Covalent organic frameworks (COFs) with well-tailored channels have the potential to efficiently transport ions yet remain to be explored. The ion transport capability is generally limited due to the lack...

Organic semiconductor lasers (OSLs) have emerged as particularly challenging. One of the major issues preventing the successful realization of lasing from organic emitters under electrically pumped conditions is the inevitable population of triplet excitons. Herein, a novel concept is presented to construct tripletsinglet guest-host gain systems with incorporating iridium complexes as the triplet sensitizers and a fluorescent conjugated polymer as the gain media to achieve light amplification. The direct triplet-singlet energy transfer process is confirmed by photoluminescence excitation spectra, photoinduced absorption spectroscopy, and fluorescence transients of the blend samples. Successful light amplification with a threefold lower amplified spontaneous emission threshold and much better lasing performance is demonstrated for the resulting tripletsinglet guest-host system as compared with the corresponding gain system without triplet sensitizers. Moreover, under electrically driven conditions, the fluorescent organic light-emitting diodes (OLEDs) based on the triplet-singlet guest-host systems with "triplet sensitizers" exhibit enhanced electrical performance relative to those without. The work suggests an effective general methodology to utilize both the singlet and triplet excitons to contribute to the light amplification with excellent electrical performance in OLEDs, opening prospects toward attempting electrically pumped OSLs.

A novel set of ladder-type poly(indenofluorene-co-benzothiadiazole)s were designed, synthesized, and explored as efficient gain media for organic lasers.