Three azahelicene derivatives with electron-rich bis(4-methoxyphenyl)amino or bis(p-methoxyphenyl)aminophenyl groups at the terminals were deliberately designed, synthesized, and characterized as hole-transporting materials (HTMs) for perovskite solar cells (PSCs). Optical and thermal properties, energy level alignments, film morphologies, hole extraction ability, and hole mobility were studied in detail. PSCs using the newly synthesized molecules as HTMs were fabricated. A maximum power conversion efficiency (PCE) of 17.34% was observed for the bis(p-methoxyphenyl)amino-substituted derivative (SY1) and 16.10% for the bis(p-methoxyphenyl)aminophenyl-substituted derivative (SY2). Longer-chain substituent such as hexyloxy group greatly diminishes the efficiency. In addition, the dopant-free devices fabricated with SY1 as the HTM shows an average PCE of 12.13%, which is significantly higher than that of spiro-OMeTAD (7.61%). The ambient long-term stability test revealed that after 500 h, the devices prepared from SY1 and SY2 retained more than 96% of its initial performance, which is much improved than the reference device with standard spiro-OMeTAD as the HTM under the same conditions. Detailed material cost analysis reveals that the material cost for SY1 is less than 8% of that for spiro-OMeTAD. These results provide a useful direction for designing a new class of HTMs to prepare highly efficient and more durable PSCs.

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A new type of star-shape polymers employing bisindolylmaleimide dye (2a-c) as the core and poly(2,7-fluorene) (PF) and/or poly(2,7-carbazole) (PC) as the arms were synthesized. These materials exhibited dual emissions consisting of an intensive blue luminescence from PF or PC and an orange emission from maleimide a result of partial energy transfer between the two. Highly efficient white light emitting devices were fabricated using a single emitting film made by spin-coating method. The electroluminescence (EL) properties of the devices were investigated from several directions, such as the loading amount of maleimide core, the concentration dependent spectral changes, the difference in the composition of arms, and the substituent effect in the indole segment, etc. A typical device based on the star-shape polymer MF001 containing 0.01 mol % of core exhibited a maximal luminous efficiency of 7.2 cd/A and external quantum efficiency of 3.2%. The device based on MMF001 with a methyl substituent on the indole group can be improved to reaching a maximal brightness of 11450 cd/m 2 , and that based on MFC1001 with arms comprising equal amount of PF and PC can be boosted to a maximal power efficiency of 4.8 lm/w. All devices can be fabricated readily and turned on at a considerable low voltage (<5 V).

An efficient hydrazine sensor was prepared based on the pyridomethene-BF 2 complex. It exhibits a high sensitivity in aqueous solutions despite the presence of a wide variety of anions and cations. It can also be fabricated into a solid state sensor for detection of hydrazine vapor. The fluorescence response of this sensor exhibits a ratiometric character at two different wavelengths, therefore significantly enhances the reliability of measurements. The sensing mechanism is well rationalized with the aid of DFT calculations.

The synthesis, dual fluorescence, and fluoroionophoric behavior of two donor-sigma spacer-acceptor (D-s-A) compounds, trans-4-(N,N-bis(2-pyridyl)amino)methylstilbene (1H) and trans-4-(N,N-bis(2-pyridyl)amino)methyl-4'-cyanostilbene (1CN), are reported and compared to that of trans-4-(N,N-bis(2-pyridyl)amino)methyl-4'-(N,N-dimethylamino)stilbene (1DPA). To gain insights into the dual fluorescence properties for 1H and 1CN in polar but not in nonpolar solvents, model compounds resulting from a replacement of the stilbene group by alkyl (2R) or xylyl (2X) groups or from a replacement of the dipyridylamino (dpa) group by dianisoleamino (3AA), diethylamino (3EE), methylanilino (3MP), or diphenylamino (3PP) groups also have been investigated. In addition to 1H and 1CN, all four compounds of 3 display dual fluorescence. The locally excited (LE) fluorescence mainly results from the stilbene group and the ICT fluorescence from the through-bond interactions between the amino donor and the stilbene acceptors. In the presence of transition metal ions such as Zn(II), Ni(II), Cu(II), and Cd(II), the ICT processes are switched from dpa (D) --> stilbene (A) in 1H and 1CN to stilbene (D) --> dpa/metal ion (A) in their complexes. Whereas the ICT states for the complexes are generally nonfluorescent, an exception was found for the case of 1H/Zn(II). As a result, substituent-dependent fluoroionophoric behavior has been demonstrated by 1H, 1CN, and 1DPA in response to Zn(II).