Synthesis And Optoelectronic Properties Of Alcohol-soluble Amino-functionalized Conjugated Organics/Polymers

Polymer light-emitting diodes (PLEDs) and polymer solar cells (PSCs), have attractedconsiderable attention over the past decades due to their unique characteristics, such as lowcost, light weight, and possible flexibility and large-area coverage. Both PLEDs and PSCsusually adopt a basic architecture composed of a thin layer of organic semiconductingmaterial sandwiched between two electrodes. It is therefore important to control theproperties and Ohmic contact of the organic/electrode interface to maximize performance.Amino-functionalized conjugated polymers (AFCPs) have exhibited wide applications owingto their excellent optoelectronic properties, orthogonal solvent processibility, and outstandinginterfacial modification functions. Combined these advantages, high efficiency and stablePLEDs and PSCs based on AFCPs cathode interlayer have been realized. That directly leadedto the realization of the first high efficiency all-solution processed PLEDs based on Ag pastecathode. Single junction PSCs based on AFCPs cathode interlayer reached PCEs of up to9.2%, which is one of the highest PCEs for single junction PSCs.The studies demonstrated in this thesis are the development of novel multifunctionalamino-functionalized conjugated polymers by optimizing their backbones and side chains.The novel amino-functionalized conjugated polymers were successfully applied in polymerlight emitting diodes and polymer solar cells.In chapter2, a series of novel crosslinkable alcohol soluble conjugated polymers(PF6N-OX, PF3N-OX, PF6N-St) containing oxetane/styrene groups and aminoalkyl groupsin the side chains have been developed and used as highly efficient electroninjection/extraction and transporting material for PLEDs and PSCs. The unique solubility inpolar solvents and crosslinkable ability of the novel conjugated polymers render them a goodcandidate for solution processed multilayer and inverted PLEDs and PSCs.It was found that novel conjugated polymers (PF6N-OX, PF6N-St) can greatly enhancethe electron injection from high work-function metal cathode Al or ITO, due to its pendantamino groups, and so high efficiency and stable PLEDs have been realized. The resultingPLEDs and inverted PLEDs showed promising performance with a maximum luminance efficiency of13.53and14.8cd A-1, respectively.When the PF3N-OX was used as ITO cathode in inverted PSCs, the PSCs showedsignificantly improved performance, and the best PSCs reached PCEs of up to9%, which isone of the highest PCEs for single junction PSCs.In chapter3, a metal-based conjugated polymer PFEN-Hg with pendent amino groupswas synthesized and employed as an efficient interlayer to improve the electron transport andcollection property in high performance I-PSCs. This new polymer offers most of the desiredproperties one would consider for an efficient interface material including orthogonal solventprocessing ability, good film formation property, effective in workfunction modification ofthe ITO substrate, low optical absorption, good electron selectivity and good electrontransporting property. With these improved interfacial properties from the PFEN-Hginterlayer, I-PSCs showed very encouraging PCE of over9%, which is one of the bestreported performance for single-junction PSCs. An even more appealing feature offered bythe new interface material is the feasibility to achieve good device performance with a widerrange of film thickness, those property is good for large-area device processing.In chapter4, an amino-functionalized organoplatinum(II) complex called Pt-N wasdeveloped and utilized as an efficient Al cathode interlayer to improve the electrontransporting and collection in high performance PSCs. This new small molecule Pt-N offersmost of the desired properties one would consider for an efficient interface material includingwell-defined chemical structure, orthogonal solvent processing ability, good film formationproperty, low optical absorption, excellent electron selectivity, good hole-blocking ability. Byusing Pt-N as ETL underneath the Al cathode, the PCE values of the PSCs can be increasedfrom the initial3.62%to8.89%, benefiting from the dramatic enhancement in Voc, FF andslightly increase in Jsc. These results indicate that the amino-functionalized organoplatinum(II) complex would be a promising family of interfacial materials for highly efficient PSCs.In chapter5, a series of blue, green and red-emitting aminoalkyl functionalizedpolyfluorene derivatives containing FSO, BT and DTBT as chromophores, respectively weresynthesized. We found that the variation of molar ratio of aminoalkyl functional groups didnot significantly influence thermal stability, UV-vis absorption, photoluminescence as well as electrochemical properties of copolymers. The application of the resulted aminoalkylfunctionalized copolymers in polymer light emitting devices exhibited dual-functionincluding efficient light-emission and electron injection from Al cathode. The increase ofmolar ratio of aminoalkyl side groups leads to enhanced device performances for both greenand red-emitting copolymers, however, reduced performance for blue-emitting ones due toformation of excimer. Best device performance with the LEmaxof3.28,7.31and0.79cd A-1was achieved for devices based on blue, green and red-emitting copolymers, respectively wasachieved by using Al as cathode. The results indicated the great potential for the applicationusing this kind of aminoalkyl functionalized copolymers as efficient light emitting layer withhigh workfunction as cathode.