Key Factor Managing the Horizontal Emitting Dipole Orientation of a Thermally Activated Delayed Fluorescence Emitter in a Mixed Host

Horizontal emitting dipole orientation (EDO) of thermally activated delayed fluorescence (TADF) molecules in a mixed host was studied by altering the host materials and host composition of the mixed host to gain insight into the important parameter of the host governing the EDO of TADF emitters. Five different host materials were combined with 1,3-bis(carbazol-9-yl)benzene (mCP), demonstrating that the host–dopant interaction is crucial to the absolute value of the horizontal EDO of the TADF emitters, whereas the glass transition temperature (Tg) is the important parameter determining the EDO dependence upon host composition. The mixed host of mCP with a high Tg host maintained high horizontal EDO in the mCP poor host composition, while that of mCP with a low Tg host showed average horizontal EDO of two hosts. Therefore, the combination of a high Tg n-type host enabling a strong host–dopant interaction with the p-type host with the usage of the n-type-host-rich composition is effective to achieve high horizontal EDO in the mixed-host-based TADF emitting layer

Hybridized Local and Charge-Transfer Excited-State Emitter for a Blue Organic Solid-State Laser

The use of triplet excitons harvesting and short exciton lifetime organic emitters is important to improve the exciton utilization in organic semiconductor laser diodes. In this study, a hybridized local and charge-transfer (HLCT)-type molecule, 11-(3-(10-(4-(1-phenyl-1H-phenanthro[9,10-d]imidazol-2-yl)phenyl)anthracen-9-yl)phenyl)-11H-benzofuro[3,2-b]carbazole (PhAnMBf), is used as an emitter for blue-emitting organic solid-state lasers (OSSLs). The short exciton lifetime and high photoluminescence quantum yield of the PhAnMBf emitter allowed the fabrication of an organic laser with an emission wavelength of 453 nm, a small full width at half-maximum of 1.2 nm, and a threshold of 105 nJ/pulse, corresponding to 44 μJ/cm2, on the distributed feedback substrate. The anthracene-based PhAnMBf material showed the potential of the HLCT emitter as an OSSL

Composition-Dependent Optoelectronic Properties of Mixed 2D/3D Metal Halide Perovskite Films for Light-Emitting Diodes

Low-dimensional perovskites with large organic cations have shown great potential for boosting the luminescence efficiency of metal halide perovskite light-emitting diodes (PeLEDs). Although numerous successful results have been obtained for mixed two-dimensional (2D)/three-dimensional (3D) perovskite films, the correlation of the optoelectronic properties with the crystallographic properties and film composition remains elusive. Herein, we investigated the optoelectronic quality of thin films and their impact on luminescence and transport behaviors in a mixed 2D/3D perovskite system containing 2D butylammonium lead bromide (BA2PbBr4) and 3D formamidinium lead bromide (FAPbBr3). Ultrafast transient absorption and temperature-dependent photoluminescence measurements revealed distinct changes in nonemissive decay of the excited states, including the vibrational coupling properties. These behaviors could then be closely correlated with the crystallographic evolution of the perovskite films. We rationalized the performance of PeLED devices and determined the possible limitations to further utilize the advantageous properties of mixed 2D/3D perovskite systems by examining both the luminescence and electrical properties of the perovskite films