All inorganic perovskites quantum dots (PeQDs) have attracted much attention for used in thin film display applications and solid-state lighting applications, owing to their narrow band emission with high photoluminescence quantum yields (PLQYs), color tunability, and solution processability. Here, we fabricated low-driving-voltage and high-efficiency CsPbBr PeQDs light-emitting devices (PeQD-LEDs) using a PeQDs washing process with an ester solvent containing butyl acetate (AcOBu) to remove excess ligands from the PeQDs. The CsPbBr PeQDs film washed with AcOBu exhibited a PLQY of 42%, and a narrow PL emission with a full width at half-maximum of 19 nm. We also demonstrated energy level alignment of the PeQD-LED in order to achieve effective hole injection into PeQDs from the adjacent hole injection layer. The PeQD-LED with AcOBu-washed PeQDs exhibited a maximum power efficiency of 31.7 lm W and EQE of 8.73%. Control of the interfacial PeQDs through ligand removal and energy level alignment in the device structure are promising methods for obtaining high PLQYs in film state and high device efficiency.

Deep‐blue fluorescent compounds are particularly important in organic light‐emitting devices (OLEDs). A donor–accepotor (DA)‐type blue‐emitting compound, 1‐(10‐(4‐methoxyphenyl)anthracen‐9‐yl)‐4‐(10‐(4‐cyanophenyl)anthracen‐9‐yl)benzene (BD3), is synthesized, and for comparison, a nonDA‐type compound, 1,4‐bis(10‐phenylanthracene‐9‐yl)benzene (BD1) and a weak DA‐type compound, 1‐(10‐phenylanthracen‐9‐yl)‐4‐(10‐(4‐cyanophenyl)anthracen‐9‐yl)‐benzene (BD2), are also synthesized. The twisted conformations of the two anthracene units in the compounds, confirmed by single crystal X‐ray analysis, effectively prevent π‐conjugation, and the compound shows deep‐blue photoluminescence (PL) with a high PL quantum efficiency, almost independent of the solvent polarity, resulting from the absence of an intramolecular charge transfer state. The DA‐type molecule BD3 in a non‐doped device exhibits a maximum external quantum efficiency (EQE) of 4.2% with a slight roll‐off, indicating good charge balance due to the DA‐type molecular design. In the doped device with 4,4′‐bis(N‐carbazolyl)‐1,1′‐biphenyl (CBP) host, the BD3 exhibits higher EQE than 10% with Commission International de L'Eclairge (CIE) coordinates of (0.15, 0.06) and a narrow full‐width at half‐maximum of 45 nm, which is close to the CIE of the high definition television standard blue.

Singlet fission of thienoquinoid compounds in organic photovoltaics is demonstrated. The escalation of the thienoquinoid length of the compounds realizes a suitable packing structure and energy levels for singlet fission. The magnetic-field dependence of the photocurrent and the external quantum efficiency of the devices reveal singlet fission of the compounds and dissociation of triplet excitons into charges.

Poly(N-vinylcarbazole) undergoes cross-linking to highly solvent-resistant films through an oxidative coupling reaction, for which an annealing process takes only 3 min at 110 °C. This reaction allows the construction of a solution-processed multilayer OLED without a time-consuming annealing process. The maximum external quantum efficiency reaches 18%, and remains at 17%, even at a high brightness of 10 000 cd m(-2) for all-solution-processed blue OLEDs.

A series of dialkylated dinaphtho­[2,1-b:2′,1′-f]­thieno­[3,2-b]­thiophenes (S-DNTTs) featuring an S-shaped sinuous π-core substituted with different alkyl chains were developed as versatile p-type organic semiconductors. The effects of the crooked shape of the π-core and the length of the flexible alkyl chains on the solution processability, thermal durability, self-organization ability, and charge-transport functionality were systematically investigated. Because the newly developed dialkylated S-DNTTs show relatively high solubilities in organic solvents, high-performing organic field-effect transistors (OFETs) can be fabricated using both dip-coating and vacuum-deposition techniques. It was revealed that the OFET performance for dialkylated S-DNTTs was significantly affected by subtle variations in the alkyl chain length. Consequently, among this family, S-DNTT-10 with longer decyl groups achieved the highest field-effect hole mobilities of up to 11 and 3.5 cm2 V–1 s–1 with on/off current ratios of over 107 in the dip-coated and vacuum-deposited OFETs, respectively. In addition, the high OFET performance of the S-DNTT-10-based system can be preserved for more than three months under ambient conditions, demonstrating its long-term stability and high durability. As revealed by two-dimensional grazing incidence X-ray diffraction analyses, a simple dip-coating method can induce unidirectional molecular orientation/assembly and thereby produce highly oriented single-crystalline domains, leading to such high hole mobilities exceeding 10 cm2 V–1 s–1 in the dip-coated OFETs.