Photomultiplication‐type organic photodetectors (PM‐OPDs) with high external quantum efficiency (EQE) of over 100% are attracting increasing attention due to their potential importance in detecting weak incident light. Considering that the gain of PM‐OPD is determined by the ratio of carrier lifetime over carrier transit time, a systematic study on the effect of the end‐functionalization of a new extended aromatic fused‐ring non‐fullerene acceptor (NFA) on the carrier trap/transit time of the PM‐OPD. Photophysical analyses by means of ultraviolet‐visible absorption, ultraviolet photoelectron spectroscopy, and photoluminescence combined with structural analyses through grazing‐incidence wide‐angle X‐ray scattering show that fluorination of the NFA with the deepest lowest unoccupied molecular orbital level and non‐isotropic molecular ordering can yield the longest carrier lifetime. Furthermore, surface energy study show that fluorination of the NFA can also yield the most hydrophobic nature, which can allow the most efficient injection barrier thinning/lowering of the active layer/cathode interface under illumination due to the localized acceptor distribution toward cathode, maximizing the hole injection efficiency from cathode. As a result, an unprecedentedly high EQE of 156 000% is obtained from the optimized PM‐OPD. This work shows the importance of the molecular design of acceptor molecules in fabricating high‐performance PM‐OPDs.

Three new anthracene-cored molecules, 3,3′-(5-(10-(naphthalen-1-yl)­anthracen-9-yl)-1,3-phenylene)­dipyridine (AP3Py-Na), 3,3′-(5-(10-(naphthalen-2-yl)­anthracen-9-yl)-1,3-phenylene)­dipyridine (AP3Py-2Na), and 9,10-bis­(3,5-di­(pyridin-3-yl)­phenyl)­anthracene (ADP3Py), were synthesized to be used as an efficiency-enhancement layer (EEL) in blue fluorescent organic light-emitting diodes. Insertion of a very thin EEL (3 nm) between the deep blue emitting layer (EML) and the electron transport layer enhanced the external quantum efficiency (EQE) of the blue device by 44% compared to the device without the EEL, resulting in an EQE of 7.9% and a current efficiency of 9.0 cd A–1 at 1000 cd m–2; the CIE coordinates of the emitting color were (0.13, 0.14). The transient electroluminescence showed that the efficiency enhancement originates from the triplet–triplet annihilation (TTA) process in the EEL, followed by energy transfer to the emitting dye in the EML.

It is shown that the performance and the operational stability of an all‐polymer photomultiplication‐type organic photodiode (PM‐OPD) can be significantly enhanced by realizing near‐ideal spatial isolation of polymer acceptor via a synthetic approach. A series of new naphthalenediimide‐based D–A polymer acceptors, PNDI–Ph, PNDI–Tol, and PNDI–Xy, with different degrees of backbone planarity are synthesized. By introducing benzene, toluene, and p–xylene as the donor units, increasing intramolecular torsional angle is expected. Thus, 2D grazing‐incidence X‐ray diffraction reveals the highest paracrystalline disorder in the PNDI–Xy thin film. Furthermore, PNDI–Xy has the lowest surface energy resulting in the smallest surface energy difference with matrix donor polymer, poly(3‐hexylthiophene‐diyl) (P3HT). When combined with P3HT, the less aggregated and low surface energy nature of PNDI–Xy results in near‐ideal spatial isolation. Consequently, the all‐polymer PM‐OPD yielded a high external quantum efficiency of 770 000% with specific detectivity of 3.06 × 1013 Jones. The physics behind the success of PNDI–Xy in PM‐OPD is discussed in conjunction with temperature‐dependent current density‐voltage analyses and drift‐diffusion simulations. Furthermore, the use of polymer acceptor enables the resulting PM‐OPD to retain its performance for 24 h, with significantly improved operational stability.

Chitinases (EC 3.2.1.14) are enzymes that hydrolyze chitin by cleaving β‐1,4 N‐glycosidic bonds. These enzymes have been used for multiple applications in biotechnology, especially for controlling insect pests and phytopathogenic fungi. In the present study, we isolated two chitinase‐producing bacteria strains from insects (strain SCH‐1 from Moechotypa diphysis and strain SCH‐2 from Sphedanolestes impressicollis). Serratia sp. SCH‐1 was a short, rod‐shaped facultative anaerobe, while Bacillus strain SCH‐2 was a rod‐shaped endospore‐forming anaerobe. Strains SCH‐1 and SCH‐2 were identified as Serratia sp. and Bacillus sp., respectively based on 16S rRNA gene sequencing. Strain SCH‐1 shared maximum homology (99.44%) with Serratia nematodiphila DZ0503SBS1 and Serratia marcescens subsp. sakuensis KRED. Strain SCH‐2 had a maximum homology of 99.24% with Bacillus thuringiensis ATCC 10792 and Bacillus toyonensis BCT‐7112. Serratia sp. SCH‐1 contained greater levels of saturated fatty acids, but the concentration of branched acids, especially iso‐C15:0, was highest in Bacillus sp. SCH‐2. Serratia sp. SCH‐1 possessed chitinase activity of 1.59 unit/mg protein after 5 days of incubation in culture medium. In contrast, Bacillus sp. SCH‐2 had a maximum activity of 0.84 unit/mg protein after 4 days of incubation. Chitinase isozymes produced by Serratia sp. SCH‐1 appeared as five bands with sizes of 20, 26, 36, 45 and 54 kDa. Bacillus sp. SCH‐2 showed a chitinase isozyme profile with three bands having sizes of 36, 45 and 50 kDa on SDS‐PAGE gels.

Organic light-emitting diodes (OLEDs) have become mainstream as the next generation of wearable displays that will outperform lasers and light-emitting diodes (LEDs). Recently, OLED-based platforms used for light applications were introduced. [1][2][3] In particular, deep red to nearinfrared (DR/NIR) OLEDs have emerged in the past few years because they can be applied for night vision displays, optical sensors, and phototherapy. [4] However, DR/NIR emitters exhibit intrinsic defects: these emitters are prone to undesired nonradiative decay pathways owing to the narrow bandgap. According to the energy gap law, the nonradiative decay rate (k nr ) is inversely proportional to the bandgap. In addition to this, the radiative rate (k r ) has a cubic dependence on the transition energy, so that it is expected to get smaller for lower energy emitters, implying that DR/NIR emitters have poor quantum efficiencies because of the incorporation of ground-and excited-vibrational energy states. [5][6][7][8][9] Consequently, research on high efficiency DR/NIR OLEDs has lagged behind that on visible-region OLEDs. To overcome this limitation, diverse ways of boosting the DR/NIR efficiency were introduced. In general, there are three kinds of DR/NIR emitters for high efficiency DR/NIR OLEDs: donor-acceptordonor (D-A-D) type, [10,11] thermally activated delayed fluorescence (TADF), [12][13][14][15] and transition-metal complexes. [16,17] DR/ NIR fluorophores of the D-A-D type have been researched to provide DR/NIR OLEDs with cost advantage and versatility. However, most DR/NIR OLEDs based on the D-A-D type show extremely low external quantum efficiency (EQE), radiance, and unexplained operational lifetime for practical application. [10,11] TADF DR/NIR emitters utilize nonradiative triplet excitons that move to a singlet region and achieve 100% internal quantum efficiency (IQE). [18] Nonetheless, there are chronic constraints with fluorescence quenching. Therefore, TADF-based DR/NIR OLEDs have a low luminance value. Meanwhile, high-efficiency DR/NIR OLEDs using transition metal complexes such as osmium (Os), [19][20][21] platinum (Pt), [22][23][24][25][26] and iridium (Ir) [27][28][29][30][31][32][33][34][35][36][37][38]