Synthesis And Photoelectric Properties Of Novel Water/Alcohol-soluble Conjugated Small Molecules/polymers

Conjugated small molecules/polymers have been widely used in organic electronic devices,such as organic light-emitting diodes,organic photovoltaics(OPVs)and perovskite solar cells(PvSCs),as a result of their significant advantages including light weight,low cost,flexibility,solution processing,and feasible photoelectric properties tuning by structure modification.Among them,water/alcohol-soluble conjugated small molecules(WSCMs)and polymers(WSCPs)have attracted scientists’ great attention due to their unique solubility,good photoelectric properties and efficient interface modification ability for photoelectric devices.Our researches are focus on the synthesis and photoelectric properties of novel WSCMs and WSCPs.In chapter 2,a new WSCM named as FPyBr based on bispyridinium salt,which shows combined properties of high electronic affinity(EA)and ionization energy(IP),excellent alcohol solubility,nice film-forming ability and high Br-content,was developed.When it was used as cathode interlayer(CIL)in CH3NH3PbI3/fullerene based PvSCs,its lowest unoccupied molecular orbital energy level(ELUMO)could form excellent energy level alignment at the cathode side,which promoted electron transport and collection.Besides,its deep-lying highest occupied molecular orbital energy level(EHOMO)could serve as an effective hole blocking layer.In addition,FPyBr could n-dope fullerene electron transporting layer,which promoted electron transport toward cathode.As a result,by incorporating a FPyBr CIL,high-performance and low-hysteresis PvSCs with a maximal power conversion efficiency(PCE)of 19.61% could be realized;on the contrary,the reference devices without any CIL displayed distinctly worse performance,with a maximal PCE of 16.97%.On the other hand,when FPyBr was utilized to improve the cathode interface of conventional bulk-heterojunction(BHJ)polymer solar cells(PSCs),it could also form nice ohmic contact at the cathode side and block holes from reaching the cathode.Moreover,the probable interfacial dipoles formed between FPyBr and cathode could reduce the WF of cathode and thus enhance the open circuit voltage(Voc)of PSCs.Based on these functions,FPyBr could increase the PCE by 40.4%.In chapter 3,novel WSCMs and WSCP based on dibenzothiophene-S,S-dioxide(FSO)and bispyridinium/bispyrimidinium were designed and synthesized.The WSCMs own high EA,excellent water solubility and planar rigidity,while the WSCP(PFSOPyCl)shows combined characters of high EA and IP,good solubility in high polarity organic solvents and fine film-forming ability.When PFSOPyCl was used as CIL in conventional BHJ PSCs,it could significantly increase the apparent electron mobility of PSCs.In addition,its ELUMO could form favorable energy alignment at the cathode side,while its EHOMO served as an efficient hole blocking layer.Moreover,the bispyridinium salts within the conjugated backbone of PFSOPyCl might generate interfacial dipoles with cathode,which decreased the WF of cathode and thus increased the Voc of PSCs;the Cl-anions within PFSOPyCl could n-dope fullerene acceptor,which was in favor of inducing good conductive pathway.As a result,two different PSCs with PFSOPyCl CIL both exhibited better performance than those of poly[(9,9-bis(3’-(N,N-dimethylamino)-propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)](PFN)-modified devices.These results indicated that this kind of WSCP is a promising cathode interfacial material(CIM).In chapter 4,considering the excellent cathode modification ability of amino groups and the similar chemical properties between pyridine and amino groups,we introduced pyridine groups into the side chains of fluorene unit and thus developed a series of WSCPs.We proposed that the pyridine groups in the side chains of these polymers might induce interfacial dipoles with cathode,which leaded to the reduction of cathode WF and enlargement of device Voc.Furthermore,the pyridine groups could also n-dope fullerene acceptor and thus generated more effective electron transporting pathway in the PSCs.All of these WSCPs could form smooth films atop the active layers,which were in favor of reduing the damage of active layers by cathode metal atoms.Based on above functions,all of these WSCPs could improve the performance of PSCs significantly,and the best material exhibited almost comparative modification ability with PFN.In chapter 5,in order to achieve WSCPs with good charge transporting properties,we enlarged the conjugated planarity of FSO unit and synthesized a novel amino-functionalized FSO derivative monomer.After its polymerization with other monomers,three WSCPs were obtained,and their optical and electrochemical properties were investigated.The amino groups endowed the polymers not only with solubility in methanol under the presence of small amount of acetic acid or trifluoroacetic acid,but also probably with cathode modification properties.They may be a class of promising CIMs for photoelectric devices.