Novel Solution-processed Conjugated Polymers: Synthesis And Applications In Organic Optoelectronic Devices

Polymer based organic electronic devices, such as polymer light-emitting diodes (PLEDs)and polymer solar cells (PSCs) have attracted considerable attention in recent years due totheir unique characteristics, such as low cost, light weight and potential applicability toflexible and large-area devices. Both PLEDs and PSCs usually adopt a multilayer devicestructure comprising a thin layer of polymer active material sandwiched between twoinorganic electrodes, and an interlayer was inserted between the active layer and the electrode.The polymer active layers determine the performance of devieces, and the interfacemodification layers could optimize charge-injection/extraction and improve the deviceperformance; thus in order to acquire high performance devices, it is essential to developnovel active/interlayer materials.In this thesis, we present two aspects of our thesis studies, the first topic includes themainchain or sidechain modifications in water/alcohol soluble conjugated polymers (WSCPs)to ebhance their interface modification capability in polymer optoelectronic devices; thesecond topic includes the reducing of steric hindrance caused by the alkyl chains in the9position of fluorene unit in the polymers’ backbone to improve the narrow-band-gappolyfluorene’s hole mobility and photovoltaic performance.In chapter2, a series of fluorene-triphenylamine based polyelectrolyte with differentcounter-ions were synthesized by polymer ion-exchange reactions. When used as holetransporting layer (HTL) in PF8BT based PLEDs, the choice of counter-ions had a greatinfluence on the device performance. PFN-TPA-F exhibited the best anode interfacemodification capability. While used as electron transporting layer (ETL) in P-PPV basedPLEDs, a reversed result was observed; PFN-TPA-F exhibited the worset cathode interfacemodification capability and polyelectrolytes with other counter-ions exhibited a decentcathode interface modification capability.In chapter3, a series of amino N-oxide functionalized polyfluorene homopolymer andcopolymers with pyridine (PNOs) were synthesized. The excellent solubility in polar solventsand good electron injection ability from high work-function metals of PNOs make them goodcandidates for the interface modification of solution processed multilayer polymer light-emitting diodes (PLEDs) and polymer solar cells (PSCs). PLEDs and PSCs usingPNO/Al cathode show much better performance than those devices based on PNs/Al cathode.Especially by using PF6NO25Py as cathode interlayer, best device performance for PLEDsand PSCs were achieved, that was more than90and1.7times higher than that of bare Alcathode device for PLEDs and PSCs, respectively.In chapter4, a series of WSCPs containing highly polar groups, such as N-oxide pyridineor pyridine quaternary ammonium, in polymers’ backbone were synthesized. PSCs usingthese WSCPs as cathode interlayer adjacent to Al cathode show much better performance thanthose devices based on bare Al cathode, indicating that these materials have good cathodeinterface modification capability. However, in these WSCPs, the choice of polar groups in themainchain exhibted much less impact on the WSCPs’ interface modification capability. PSCdevices based on these WSCPs cathode interlayer exhibited nearly the same performance withthe PFN/Al cathode PSC devices.In chapter5, a series of narrow-band-gap conjugated polymers based on9-alkyl-9-H-fluorene were synthesized. The reducing number of alkyl chains in the9positionof fluorene unit in polymers’ backbone could reduce the steric hindrance caused by alkylchain. Compared with polymers based on9,9-disubstituted alkyl-fluorene, a higher holemobility was achived in these9-alkyl-9-H-fluorene based polymers, and thus exhibited ahigher FF in corresponding PSC devices. With a PF25DBT8:PC71BM active layer, best PSCdevice performance could be reached as a JSCof7.71mA/cm2, a Vocof0.90V, a FF of57.23%, and a PCE of3.97%.