RESUMO
Due to the easy formation of compact molecular packing arrangements and the favorable photophysical and electrochemical properties, donor-acceptor-donor (D-A-D)-type small molecule hole-transporting materials (HTMs) have been widely synthesized and researched to improve the efficiency and stability of perovskite solar cells (PSCs). The main approach in recent experiments has been to seek good acceptors, whereas the influence of the electron-donating units has been less reported. In this work, six new benzothiadiazole-based D-A-D-type HTMs are tailored by employing the ethyl-substituted phenoxazine (POZ), phenothiazine (PTZ) and carbazole (CZ) as the donors. To obtain an elementary understanding of new HTMs, the electronic, optical, hole-transporting and interfacial properties are simulated with quantum chemistry methods. The results indicate that all tailored HTMs exhibit suitable energy alignment compared with the band structures of the perovskite, and the continuous highest occupied molecular orbital (HOMO) levels will be helpful for interfacial energy regulation. In comparison with the YN1, the maximum absorption wavelengths of the newly designed HTMs are red-shifted due to the decreased excitation energies from the ground-state to the first singlet excited-state. Importantly, the hole mobilities of all designed HTMs are distinctly higher than the referenced YN1, which is contributed by the better planarity of the molecular skeleton and the easier orbital overlapping between adjacent molecules. The interfacial simulations manifest that the FAPbI3/SM37 system displays a more stable adsorption configuration and greater charge redistributions at the interface compared to YN1, which further promotes the separation of photogenerated electron-hole pairs. Moreover, larger Stokes shifts and better solubility are also acquired for the new HTMs. In summary, our calculations not only propose several potential highly efficient HTMs, but also provide useful insights at the atomic level for the experimental synthesis of new D-A-D-type HTMs.
RESUMO
Lead halide perovskites have been considered promising materials for optoelectronic applications owing to their superior properties. CsPbBr3 nanocrystals (NCs) with a narrow particle size distribution and a narrow emission spectrum are synthesized by ligand-assisted re-precipitation (LARP), a low-cost and facile process. In inverted CsPbBr3 NC LEDs, a dual hole injection layer (HIL) of 1,4,5,8,9,11-hexaazatriphenylene-hexacarbonitrile (HAT-CN)/MoO3 is introduced to enhance hole injection and transport, because HAT-CN can extract electrons easily from the hole transport layer and leave a large number of holes there. The current and power efficiencies of the optimized device with a dual HIL are 1.5- and 1.8-fold higher than those of the single HIL device. It is believed that the dual HAT-CN/MoO3 HIL effectively promotes hole injection and has promise for application in many other devices.
RESUMO
A series of divalent and oxabridged neonicotinoids were synthesized by reactions of nitromethylene analogues of imidacloprid and dialdehydes, and their structures were confirmed by (1)H NMR, (13)C NMR, high-resolution mass spectroscopy, and X-ray diffraction analysis. The bioassays indicated that some of them were endowed with excellent insecticidal activities against cowpea aphid ( Aphis craccivora ), armyworm ( Pseudaletia separata Walker), and brown planthopper ( Nilaparvata lugens ). Divalent neonicotinoid 6 and oxabridged 8a had higher activities than imidacloprid against cowpea aphids and armyworm; furthermore, the activity of 8a was 40.4-fold higher than that of imidacloprid against imidacloprid-resistant brown planthopper.