Synthesis And Characterization Of Alcohol-soluble Organic Small Molecular Electrolyte For Cathode Interfacial Materials

Cathode interfacial materials(CIM) find important applications in organic optoelectronic devices such as organic light-emitting diodes(OLEDs) and organic photovoltaics(OPV). Although metal cathodes with low work function, for instance, Ca and Ba, are effective cathodes, they are vulnerable to the water and oxygen in the air, which can affect the stability and lifetime of the devices. On the other hand, environmental stable metals(e.g. Au and Ag) are favorable, but have a high work function. Therefore, the development of effective cathode interfacial materials that lower the work function of stable cathode materials(such as Ag, Al, and ITO) is particularly important.This thesis focuses on alcohol-soluble organic small molecular electrolyte in OLEDs and OPV devices, respectively as cathode interfacial materials. The results are shown below: 1) To improve the solution-processing properties of LG-2b in alcohol solvents we reported earlier, we design BFN-BF4 and FN-BF4 with different conjugation length and tetrafluoroborate(BF4–counter-anion. Compared with LG-2b, the target products are easier to be synthesized and show a higher alcohol-solubility. When applied in the green light OLED device ITO/PEDOT:PSS/PVK/Green-1a/CIM/Al(CIM = BFN-BF4, FN-BF4), they produce better performance than that of Cs F/Al.OOO OON+BF4-OOON+BF4-BFN-BF4FN-BF4OON+OOBF4-LG-2b2) Considering that BFN-BF4 and FN-BF4 are unsuitable to be interfacial layer in the inverted device due to their poor resistance to weakly polar solvent(such as toluene and chlorobenzene), we synthesize three heterocyclic nitrogen electrolytes Phen-Br, Phen-SO3 and Phen Na DPO-Br with larger polarity, for lowing their solubility in weakly polar solvent and increasing their resistance to weakly polar solvent. All possess simple synthetic routes and better water/alcohol solubility. Among them, Phen Na DPO-Br has the best device performance. When Phen Na DPO-Br is used as cathode interfacial layer in the conventional OPV devices ITO/PEDOT:PSS/PTB7:PC71BM/CIM/Al(CIM = Phen Na DPO-Br), a PCE of 7.60% has been obtained, which is higher than that of Al-only cathode(PCE = 4.65%). Furthermore, Phen Na DPO-Br shows higher power conversion efficiency than that of bare Zn O in the inverted OPV device ITO/Zn O/CIM/PTB7:PC71BM/Mo O3/Al(CIM = Phen Na DPO-Br).