Design And Synthesis Of Organic Photoelectronic Functional Materials Based On Spiro-Structures

Spiro-type materials are superior organic optoelectronic functional materials.Taking 9,9'-spirobifluorene(SBF)as an example,the vertical spiro-structure of SBF can effectively inhibit the ?-? stacking effect between molecules,thereby improving both the solubility in aromatic solvents(such as toluene and chlorobenzene),and the thermal properties.The excellent solubility and thermal properties respectively contribute to the formation of an excellent amorphous layer during the preparation of the devices either by spin coating or by thermal evaporationresuiting in increased efficiency in the devices.However,the electrical activity of 9,9'-spirobifluorene is poor.The introduction of different electron-withdrawing or electron-donating groups into fluorene moiety can overcome this difficulty.We find that 4-phenyl-9-carbazole has a strong electron-donating ability.When the 4-phenyl-9-carbazole and fluorene are on sides of the spiro-carbon atom,it can be used as a good electron-donating group with a high photoluminance quantum yield(PLQY).As absorbing the electron-withdrawing sulfone group into fluorene unit and replacing the other fluorene moiety with electron-donating 9'H-9,3':6',9'-tercarbazole group,it can thereby balance the carrier mobility and modulating energy levels of new hosts.The spiro-phenyl carbazole unit also has good hole-transporting properties.The derivatives at the site can improve the solubility,tune the energy levels and increase the hole-transporting ability of the material.In this paper,we have developed a series of functionalized materials,including luminescent guest materials,host materials and hole-transporting materials based on the structure of spiro-phenyl carbazole.In the second chapter,two thermally activated delayed fluorescence(TADF)deep-blue emitters(4-SCZ,4-SCZ-F)were developed by combining a novel spiro-type donor moiety with the different triazine-based unit.We have systematically studied their photophysical.thermodynamic and electroluminescence properties.By modifying the interplay between the donors and acceptor through tuning the phenylene linker using a fluorine substituent,singlet-triplet splitting(?EST)and PLQY can be regulated;when adding fluorine to the molecule,4-SCZ-F shifted the emission color by 4 nm.As a result.when applied 4-SCZ-F as the emitter in organic light-emitting diodes(OLED)device.good performance with current efficiency(CE)/power efficiency(PE)/external quantum efficiency(EQE)of 11.16 cd/A/9.74 lm/W/7.21%and Commission Internationale de l'Eclairage(CIE)coordinate at(0.16,0.17)was achieved.These results indicate that the introduction of a fluorine moiety on the phenylene bridge between the electron-withdrawing group and the electron-withdrawing group greatly contributes to the improvement of device performance of the deep-blue emitter.In the third chapter,we changed the attachment site of phenyl to carbazole and introduced the electron-donating group tercarbazole.Moreover,the electron-withdrawing sulfone group absorbed into the other side of the fluorene.As is known,9,H-9,3':6',9"-tercarbazole is an excellent electron-donating moiety and its derivatives have been widely used in blue TADF materials,However,utilizing 9'H-9,3':6',9"-tercarbazole as building-block in designing new donor spiro-type host materials in OLEDs is seldom reported.In this work,a novel spiro-configured host TCZSO2 incorporating with 9'H-9,3':6',9"-tercarbazole and 9H-thioxanthene 10,10-dioxide moieties is designed and synthesized.In particular,the full color devices based on TCZSO2/Flrpic(blue),TCZSO2/Ir(ppy)2(acac)(green)and TCZSO2/Ir(MDQ)2(acac)(red)all exhibit respectable EQEs of 22.8%,24.0%and 21.0%,respectively.More encouraging,the blue and green phosphorescent organic light-emitting diodes(PhOLEDs)have quite a low efficiency roll-off(EQE:22.7%/24.0%,FIrpic/Ir(ppy)2(acac))at a high brightness of 1000 cd m-2.At a higher brightness of 5,000 cd m-2,there are only 5.2%and 4.9%decrease in EQE from their maximum values,indicating a very low efficiency roll-off.These excellent results confirm the novel spiro-type host design strategy for incorporating electron donor reported in blue TADF materials with high triplet energy to achieve high-performance RGB PhOLEDs.In the fourth chapter,we perfectly utilized the excellent hole-transporting properties of the spiro-phenyl carbazole skeleton.designed and synthesized SCZF-5 for use in solar cells.In addition,another single-spiro hole-transporting material(HTM)SAF-5 with reported 10-phenyl-10H-spiro[acridine-9,9'-fluorene](SAF)core was also synthesized for comparison.Combined with the commercial material spiro-OMeTAD,we systematically studied the energy levels,hole mobility and device performance of the three HTMs based on different spiro cores through the tests and characterization of photochemistry,photophysical.Through varying from SAF core to SCZF core as well as comparing with the classic 9,9'-spirobifluorene,we find in perovskite solar cells that the new HTM SCZF-5 exhibits more impressive power conversion efficiency(PCE)of 20.10%than SAF-5(13.93%)and the commercial HTM spiro-OMeTAD(19.11%).On the other hand,the SCZF-5 based device also has better durability in lifetime testing,which could be related to the improvement of the hydrophobic properties of the material.These results indicate that the newly designed SCZF by integrating carbazole into the spiro-structure has good potential in developing effective HTMs for use in perovskite solar cells.