Synthesis, Properties And Application Of Novel Solution Film-forming Hole-transporting Materials

Series of small molecule hole-transporting materials?SMHTMs?have been synthesized with tetraphenylbiphenyldiamine?TPB?,triphenylamine?TPA?and naphthalene ring as the core,through the bridge foundation double bond connecting the TPA and carbazole groups.The structures of intermediates and target products have been characterized using infrared spectroscopy?IR?,nuclear magnetic resonance?NMR?spectroscopy,mass spectrometry?MS?and X-ray single crystal diffraction.All the assynthesized SMHTMs have good solubility in common solvents?tetrahydrofuran,chlorobenzene,chloroform,etc.?.Quantum chemical calculations show that the introduction of double bonds contributing to the expansion of molecular conjugate area.The "propeller" TPA units could effectively restrain crystallization and form amorphous solid films.The UV-Vis absorption spectra in the dilute tetrahydrofuran?THF?show the compounds exhibit two absorption bonds at the region of 290 310 nm and 350 450 nm,respectively.UVVis of solid films show the similar characteristics to THF solution,but slightly red shift happened duing to the molecular aggregation.The maxima emission peaks of PL are located at 430 ⁵40 nm,corresponding to blue to green light emission.These compounds have the fluorescence life between 1.5 ns and 3.0 ns,and the absolute fluorescence quantum yield are between 60% and 80% in dilute THF solution.Photoelectric yield spectroscopy?PYS?show that the HOMO levels of these compounds are in the range of-4.90 ^-5.50 eV,which could be used as an appropriate hole injection and transport of materials.Thermal properties test show that SMHTMs having good thermal stability,thermal decomposition temperature is between 290 450 °C,the glass transition temperature is between 90 170 °C.The hole mobilities are obtained by TOF method,which are 1.0×10^-5 cm2 V-1s-1 9.0×10^-4 cm2 V-1s-1 under 1.0×10⁵ 2.0×10⁵ V cm-1 electric field intensity.The as-synthesized compounds were applied in the all-solution prepared flexible green light OLED devices: ITO/HTM/P-PPV/Ba/Al,compared with the devices based on PEDOT:PSS,the devices based on SMHTMs exhibit the lower turn-on voltage?3.25 V?,higher luminous(103690 cd m^-2)and the "efficiency roll-off" are effectively inhibited."Wet process" is applied to Alq3 green devices: ITO/HTM/Alq3/LiF/Al,the devices based on SMHTMs showing the higher luminous(5144 cd m^-2)and the lower working voltage?8.16 V?compared to TPD-based devices.As hole-transporting and light-emitting materials?HT-EMs?applied in simple-structured OLED: ITO/PEDOT/HT-EMs/PFN/Al,when the electrodes were modified by PEDOT and PFN,the devices showed 2.70 V and 2010 cd m^-2 for turn-on voltage and the maximum luminous,respectively.And with the increase of working voltage,the changes of electroluminescent spectral were almost negligible,illustrating the stabilized working characteristics.As HTMs applied in the perovskite solar cells?PSC?with mesoporous structure.Compared with spiro-OMeTAD,the PSCs based on SMHTMs show the better Voc?927.6 mV?,Jsc(17.37 mA cm^-2),FF?0.73?and PCE?11.06%?.When doped with Co?TFSI?2?5%?,PSCs show the PCE of 11.62%,which is slightly lower than those based on spiro-OMeTAD-doped.But batteries based on SMHTMs-doped showed more stable performance after 600 hours operation compared with spiro-OMeTAD-doped.